Glass articles having films with moderate adhesion and retained strength

ABSTRACT

One or more aspects of the disclosure pertain to an article including a film disposed on a glass substrate, which may be strengthened, where the interface between the film and the glass substrate is modified, such that the article has an improved average flexural strength, and the film retains key functional properties for its application. Some key functional properties of the film include optical, electrical and/or mechanical properties. In one or more embodiments, the interface exhibits an effective adhesion energy of about less than about 4 J/m 2 . In some embodiments, the interface is modified by the inclusion of a crack mitigating layer containing an inorganic material between the glass substrate and the film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims the benefit of priorityunder 35 U.S.C. §120 of U.S. Pat. No. 9,725,357 granted Aug. 8, 2017,which is a continuation-in-part of and claims the benefit of priorityunder 35 U.S.C. §120 of U.S. Pat. No. 9,586,858 granted on Mar. 7, 2017,which claims the benefit of priority under 35 U.S.C. §119 of U.S.Provisional Application Ser. No. 61/820,395 filed on May 7, 2013 and thebenefit of priority under 35 U.S.C. §119 of U.S. Provisional ApplicationSer. No. 61/712,908 filed on Oct. 12, 2012, the contents of which arerelied upon and incorporated herein by reference in their entirety.

BACKGROUND

This disclosure relates to articles including laminates with a glasssubstrate that has a film disposed on its surface, and a modifiedinterface between the film and the glass substrate such that the glasssubstrate substantially retains its average flexural strength, and thefilm retains key properties for its application.

Articles including a glass substrate, which may be strengthened orstrong as described herein, have found wide usage recently as aprotective cover glass for displays, especially in touch-screenapplications, and there is a potential for their use in many otherapplications, such as automotive or architectural windows, glass forphotovoltaic systems and glass substrates for use in other electronicdevice applications. In many of these applications it can beadvantageous to apply a film to the glass substrates. Exemplary filmsinclude indium-tin-oxide (“ITO”) or other transparent conductive oxides(e.g., aluminum and gallium doped zinc oxides and fluorine doped tinoxide), hard films of various kinds (e.g., diamond-like carbon, Al₂O₃,AlN, AlO_(x)N_(y), Si₃N₄, SiO_(x)N_(y), SiAl_(x)O_(y)N_(z), TiN, TiC),IR or UV reflecting layers, conducting or semiconducting layers,electronics layers, thin-film-transistor layers, or anti-reflection(“AR”) films (e.g., SiO₂, Nb₂O₅ and TiO₂ layered structures). In manyinstances these films must necessarily be hard and/or have a highelastic modulus, or otherwise their other functional properties (e.g.,mechanical, durability, electrical conductivity, optical properties)will be degraded. In most cases these films are thin films, that is,they generally have a thickness in the range of 0.005 μm to 10 μm (e.g.,5 nm to 10,000 nm).

When a film is applied to a surface of a glass substrate, which may bestrengthened or characterized as strong, the average flexural strengthof the glass substrate may be reduced, for example, when evaluated usingball-drop or ring-on-ring strength testing. This behavior has beenmeasured to be independent of temperature effects (i.e., the behavior isnot caused by significant or measurable relaxation of surfacecompressive stress in the strengthened glass substrate due to anyheating). The reduction in average flexural strength is also apparentlyindependent of any glass surface damage or corrosion from processing,and is apparently an inherent mechanical attribute of the article, evenwhen thin films having a thickness in the range from about 5 nm to about10 μm are applied to the article. Without being bound by theory, thisreduction in average flexural strength is believed to be associated withthe adhesion between such films relative to the strengthened or strongglass substrates, the initially high average flexural strength (or highaverage strain-to-failure) of selected strengthened or strong glasssubstrates relative to selected films, together with crack bridgingbetween such a film and the glass substrate.

When these articles employing glass substrates are employed in certainelectronic device applications, for example, they may be subjected toadditional high temperature processing during manufacturing. Morespecifically, the articles can be subjected to additional thermaltreatments after deposition of the film on the glass substrates. Theseadditional high temperature treatments often are the result ofapplication-specific development of additional structures and componentson the substrates and/or films of the article. Further, the depositionof the film itself on the substrate can be conducted at relatively hightemperatures.

In view of these new understandings, there is a need to prevent filmsfrom reducing the average flexural strength of glass substrates in thesearticles. There is also a need to ensure that the average flexuralstrength of the glass substrates is substantially retained, even afterhigh temperature exposures from film deposition processes and additionalapplication-specific thermal treatments.

SUMMARY

A first aspect of this disclosure pertains to an article (e.g., alaminate article) including a glass substrate, a crack mitigating layerdisposed on a first major surface of the glass substrate forming a firstinterface and a film disposed on the crack mitigating layer forming asecond interface. In one or more embodiments, the glass substrate has anaverage strain-to-failure that is greater than the averagestrain-to-failure of the film. In one or more embodiments, the firstinterface and/or the second interface exhibit have a moderate adhesionsuch that at least a portion of the crack mitigating layer separatesfrom the film or the glass substrate when the article is strained to astrain level between the average strain-to-failure of the glasssubstrate and the average strain-to-failure of the film. In a particularembodiment, at least a portion of the crack mitigating layer separatesfrom the film when a crack originating in the film bridges into thecrack mitigating layer (e.g., an adhesive failure at the interfacebetween the film and the crack mitigating layer). In another embodiment,at least a portion of the crack mitigating layer separates from theglass substrate when a crack originating in the glass substrate bridgesinto the crack mitigating layer (e.g., an adhesive failure at theinterface between the glass substrate and the crack mitigating layer).In one or more embodiments, the crack mitigating layer causes a crackoriginating in one of the film and the glass substrate and entering intothe crack mitigating layer to remain within the crack mitigating layer,or substantially within the crack mitigating layer (e.g., a cohesivefailure in the crack mitigating layer). In one or more embodiments, thecrack mitigating layer effectively confines a crack originating in oneof the film and glass substrates from propagating into the other of suchfilm and glass substrate.

In one or more embodiments, the crack mitigating layer has a fracturetoughness that is about 50% or less than the fracture toughness of oneof the glass substrate and the film. For example, the fracture toughnessof the crack mitigating layer may be about 1 MPa·m^(1/2) or less. Thethickness of the crack mitigating layer may be about 100 nm or less,about 20 nanometers or less or, in some instances, about 5 nm or less.The crack mitigating layer of one or more embodiments may be acontinuous layer or a discontinuous layer.

The crack mitigating layer may include a plasma-polymerized polymer, asilane or a metal. Examples of a plasma-polymerized polymer include aplasma-polymerized fluoropolymer, a plasma-polymerized hydrocarbonpolymer, a plasma-polymerized siloxane polymer and a plasma-polymerizedsilane polymer. The plasma-polymerized hydrocarbon polymer may be avacuum-deposited material formed from a volatile gas (e.g., an alkane(C_(n)H_(2n+2)), an alkene (C_(n)H_(2n)) and/or an alkyne(C_(n)H_(2n−2)), where n<8) and optionally hydrogen. In another variant,the crack mitigating layer may include a plasma-polymerizedfluoropolymer that includes a vacuum-deposited material formed from apolymer-forming fluorocarbon gas (e.g., CHF₃ and C₄F₈) and a fluorinatedetchant (e.g., CF₄, C₂F₆, C₃F₈, NF₃, and SF₆). Accordingly, the crackmitigating layer may include fluorine. In some embodiments, the fluorinecan be derived from a fluorine-containing gas (e.g., CHF₃, C₄F₈, CF₄,C₂F₆, C₃F₈, NF₃, and SF₆).

In yet another variant, the crack mitigating layer may include aplasma-polymerized silane polymer including a vacuum-deposited materialformed from a silane source material (e.g., a silane source materialcomprising the formulation R_(x)SiX_(4−x) where R is an alkyl or arylorganic group and X is hydrogen, a halide, and/or an alkoxy group) andan optional oxidizer (e.g., oxygen, ozone, nitrous oxide, carbondioxide, water vapor, and/or hydrogen peroxide). In one or moreembodiments, the crack mitigating layer includes a silane that is eithersolution-deposited or vapor-deposited, without the use of plasma. Thesilane may include an aliphatic silane and/or an aromatic silane. Thesilane may optionally include the formulation R_(x)SiX_(4−x) where R isa fluorine, an alkyl, an optionally-fluorinated aryl organic group or achlorinated aryl organic group, and X is a halide or an alkoxy group. Inone or more embodiments, the crack mitigating layer may include Au or Cuor may optionally include a porous layer (e.g., porous silica).

In some embodiments, the crack mitigating layer may include a metalfluoride. According to certain embodiments, the crack mitigating layercan be formed as a nanoporous layer that includes an inorganic material.In some cases, the crack mitigating layer includes an inorganicmaterial. The inorganic material can be a metal fluoride (e.g., CaF₂,BaF₂, AlF₃, MgF₂, SrF₂, LaF₃, YF₃, and lanthanide series trifluorides)in some embodiments. The inorganic material can also include a reactionproduct derived at least in part from the glass substrate.

In one or more embodiments, the film may exhibit one or more functionalproperties (e.g., optical properties, electrical properties and/ormechanical properties), which are substantially the same or retainedwhen combined with the crack mitigating layer (prior to any subsequentseparation of the crack mitigating layer from the film and/or glasssubstrate, as described herein). The film may include transparentconductive oxide layers, IR reflecting layers, UV reflecting layers,conducting layers, semiconducting layers, electronics layers, thin filmtransistor layers, EMI shielding layers, anti-reflection layers,anti-glare layers, dirt-resistant layers, self-cleaning layers,scratch-resistant layers, barrier layers, passivation layers, hermeticlayers, diffusion-blocking layers, and/or fingerprint-resistant layers.

In one or more embodiments, the glass substrate has an average flexuralstrength that is substantially maintained when combined with the crackmitigating layer and the film. The glass substrate may include an alkalialuminosilicate glass, an alkali containing borosilicate glass and/or analkali aluminoborosilicate glass. In some embodiments, the glasssubstrate may be chemically strengthened and may exhibit a compressivestress greater than about 500 MPa and a compressive depth-of-layergreater than about 15 μm.

In one or more embodiments, the article (e.g., a laminate article) hasan average flexural strength that that is substantially improved whencompared to an article comprising the glass substrate and the film butno crack mitigating layer. In some embodiments, the article exhibits aneffective adhesion energy at one or more of the first interface and thesecond interface of less than about 4 J/m², or even less than about 0.85J/m². In some embodiments, the effective adhesion energy at one or moreof the first interface and the second interface is between about 0.1J/m² and about 0.85 J/m², or between about 0.3 J/m² and about 0.7 J/m².A second aspect of this disclosure pertains to a method of forming anarticle (e.g., a laminate article). In one or more embodiments, themethod includes providing a glass substrate, disposing a film having oneor more functional properties a first opposing major surface forming aninterface with the glass substrate, and controlling the effectiveadhesion energy of the interface to less than about 4 J/m². In one ormore embodiments, the method includes controlling the effective adhesionenergy by disposing a crack mitigating layer between the film and theglass substrate. The crack mitigating layer can include fluorine and, insome cases, may further include a metal. According to some embodiments,the crack mitigating layer includes a metal fluoride having thefluorine. The crack mitigating layer can also include an inorganic metalfluoride compound that contains the fluorine. In some embodiments, thefluorine can be derived from a fluorine-containing gas (e.g., CHF₃,C₄F₈, CF₄, C₂F₆, C₃F₈, NF₃, and SF₆). According to some otherembodiments, the step for controlling the effective adhesion energy ofthe interface can include a step for effecting a reaction between thefluorine-containing gas and the substrate such that the metal in thecrack mitigating layer is derived at least in part from the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a laminate article comprising a glasssubstrate, a film and a crack mitigating layer, according to one or moreembodiments.

FIG. 2 is a schematic diagram of the development of a crack in a filmand its possible bridging modes.

FIG. 3 is an illustration of the theoretical model for the presence of acrack in a film and its possible bridging as a function of elasticmismatch α.

FIG. 4 is a diagram illustrating the energy release ratio G_(d)/G_(p).

FIG. 5A shows a top view of the glass substrate and an alternativeembodiment of the crack mitigating layer shown in FIG. 1, beforedisposing the film on the crack mitigating layer.

FIG. 5B shows a cross-sectional view of the glass substrate and crackmitigating layer shown in FIG. 5A, taken along lines 1B-1B.

FIG. 5C shows a top view of the glass substrate and an alternativeembodiment of the crack mitigating layer shown in FIG. 1, beforedisposing the film on the crack mitigating layer.

FIG. 6 is a graph presenting ring-on-ring load-to-failure performance ofglass substrates or articles according to an aspect of this disclosuregiven by Examples 1A-1E.

FIG. 7 is a graph presenting ring-on-ring load-to-failure performance ofglass substrates or articles according to an aspect of this disclosuregiven by Examples 2A-2E.

FIG. 8 is a graph presenting ring-on-ring load-to-failure performance ofglass substrates or articles according to as aspect of this disclosuregiven by Examples 2A and 2F-2H.

FIG. 9A is a schematic diagram of a cohesive failure in a crackmitigating layer according to an aspect of this disclosure.

FIG. 9B is a schematic diagram of adhesive failures associated with acrack mitigating layer according to an aspect of this disclosure.

FIG. 10A is a graph of carbon and fluorine x-ray photoelectronspectroscopy (“XPS”) data for various plasma-assisted treatments of aglass surface employing fluorine-containing gases according to a furtheraspect of this disclosure.

FIG. 10B is a graph of oxygen, silicon and aluminum XPS data for variousplasma-assisted treatments of a glass surface employingfluorine-containing gases according to an aspect of this disclosure.

FIG. 11 is a graph of XPS data for a control glass and glass subjectedto plasma-assisted treatments employing an etching gas (carbontetrafluoride) according to an aspect of this disclosure.

FIG. 12 is a graph of adhesion energy as a function of temperature forglass surfaces subjected to various plasma-assisted treatments employingfluorine-containing gases, as bonded to another glass surface, accordingto an aspect of this disclosure.

FIG. 13 is a graph of adhesion energy as a function of temperature forglass, silica and alumina surfaces on glass substrates subjected tovarious fluorine-containing surface treatments, as bonded to anotherglass surface, according to a further aspect of this disclosure.

FIG. 14 is a graph presenting ring-on-ring load-to-failure performanceof glass substrate controls and substrates having chromium films andcalcium fluoride crack mitigating layers according to an aspect of thisdisclosure given by Examples 14A-14C4.

FIG. 15 is a graph presenting ring-on-ring load-to-failure performanceof glass substrate controls and substrates having chromium films andbarium fluoride crack mitigating layers according to an aspect of thisdisclosure given by Examples 15A-15C2.

FIG. 16 is a graph presenting ring-on-ring load-to-failure performanceof glass substrate controls and substrates having chromium films andmagnesium fluoride crack mitigating layers according to an aspect ofthis disclosure given by Examples 16A-16C.

FIG. 17 is a graph presenting ring-on-ring load-to-failure performanceof glass substrate controls and substrates having indium tin oxide filmsand calcium fluoride crack mitigating layers according to an aspect ofthis disclosure given by Examples 17A-17C.

FIG. 18 is a graph presenting ring-on-ring load-to-failure performanceof glass substrate controls and substrates having indium tin oxide filmsand barium fluoride crack mitigating layers according to an aspect ofthis disclosure given by Examples 18A-18C2.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details may beset forth in order to provide a thorough understanding of embodiments ofthe disclosure. However, it will be clear to one skilled in the art whenembodiments of the disclosure may be practiced without some or all ofthese specific details. In other instances, well-known features orprocesses may not be described in detail so as not to unnecessarilyobscure the disclosure. In addition, like or identical referencenumerals may be used to identify common or similar elements.

Referring to FIG. 1, aspects of this disclosure include a laminatearticle 100 including a film 110 and a glass substrate 120 wherein theinterfacial properties between the film 110 and the glass substrate 120at the effective interface 140 are modified such that the articlesubstantially retains its average flexural strength, and the filmretains key functional properties for its application. In one or moreembodiments, the laminate article exhibits functional properties thatare also retained after such modification. Functional properties of thefilm and/or article may include optical properties, electricalproperties and/or mechanical properties, such as hardness, elasticmodulus, strain-to-failure, abrasion resistance, scratch resistance,mechanical durability, coefficient of friction, electrical conductivity,electrical resistivity, electron mobility, electron or hole carrierdoping, optical refractive index, density, opacity, transparency,reflectivity, absorptivity, transmissivity and the like. Thesefunctional properties of the film are retained after combination withthe crack mitigating layer, before any separation of the crackmitigating layer from the film and/or glass substrate as describedherein.

In one or more embodiment, the modification to the effective interface140 between the film 110 and the glass substrate 120 includes preventingone or more cracks from bridging from one of the film 110 or the glasssubstrate 120 into the other of the film 110 or the glass substrate 120,while preserving other functional properties of the film 110 and/or thearticle. In one or more specific embodiments, as illustrated in FIG. 1,the modification of the interfacial properties includes disposing acrack mitigating layer 130 between the glass substrate 120 and the film110. In one or more embodiments, the crack mitigating layer 130 isdisposed on the glass substrate 120 and forms a first interface 150, andthe film 110 is disposed on the crack mitigating layer 130 forming asecond interface 160. The effective interface 140 includes the firstinterface 150, the second interface 160 and/or the crack mitigatinglayer 130.

The term “film”, as applied to the film 110 and/or other filmsincorporated into the laminated article 100, includes one or more layersthat are formed by any known method in the art, including discretedeposition or continuous deposition processes. Such layers may be indirect contact with one another. The layers may be formed from the samematerial or more than one different material. In one or more alternativeembodiments, such layers may have intervening layers of differentmaterials disposed therebetween. In one or more embodiments a film mayinclude one or more contiguous and uninterrupted layers and/or one ormore discontinuous and interrupted layers (i.e., a layer havingdifferent materials formed adjacent to one another).

As used herein, the term “dispose” includes coating, depositing and/orforming a material onto a surface using any known method in the art. Thedisposed material may constitute a layer or film as defined herein. Thephrase “disposed on” includes the instance of forming a material onto asurface such that the material is in direct contact with the surface andalso includes the instance where the material is formed on a surface,where one or more intervening material(s) is between the disposedmaterial and the surface. The intervening material(s) may constitute alayer or film, as defined herein.

As used herein, the term “average flexural strength” is intended torefer to the flexural strength of a glass-containing material (e.g., anarticle and/or a glass substrate), as tested through methods such asring-on-ring, ball-on-ring, or ball drop testing. The term “average”when used in connection with average flexural strength or any otherproperty is based on the mathematical average of measurements of suchproperty on at least 5 samples, at least 10 samples or at least 15samples or at least 20 samples. Average flexural strength may refer tothe scale parameter of two parameter Weibull statistics of failure loadunder ring-on-ring or ball-on-ring testing. This scale parameter is alsocalled the Weibull characteristic strength, at which a material'sfailure probability is 63.2%. More broadly, average flexural strengthmay also be defined by other tests such as a ball drop test, where theglass surface flexural strength is characterized by a ball drop heightthat can be tolerated without failure. Glass surface strength may alsobe tested in a device configuration, where an appliance or devicecontaining the glass-containing material (e.g., an article and/or aglass substrate) article is dropped in different orientations that maycreate a surface flexural stress. Average flexural strength may in somecases also incorporate the strength as tested by other methods known inthe art, such as 3-point bend or 4-point bend testing. In some cases,these test methods may be significantly influenced by the edge strengthof the article.

As used herein, the terms “bridge”, or “bridging”, refer to crack, flawor defect formation and such crack, flaw or defect's growth in sizeand/or propagation from one material, layer or film into anothermaterial, layer or film. For example, bridging includes the instancewhere a crack that is present in the film 110 propagates into anothermaterial, layer or film (e.g., the glass substrate 120). The terms“bridge” or “bridging” also include the instance where a crack crossesan interface between different materials, different layers and/ordifferent films. The materials, layers and/or films need not be indirect contact with one another for a crack to bridge between suchmaterials, layers and/or films. For example, the crack may bridge from afirst material into a second material, not in direct contact with thefirst material, by bridging through an intermediate material disposedbetween the first and second material. The same scenario may apply tolayers and films and combinations of materials, layers and films. In thearticles described herein, a crack may originate in one of the film 110or the glass substrate 120 and bridge into the other of the film 110 orthe glass substrate 120 across the effective interface 140 (andspecifically across the first interface 150 and the second interface160). As will be described herein, the crack mitigating layer 130 maydeflect cracks from bridging between the film 110 and the glasssubstrate 120, regardless of where (i.e., the film 110 or the glasssubstrate 120) the crack originates. Crack deflection may include atleast partial delamination of the crack mitigating layer 130 from thefilm 110 and/or glass substrate 120, as described herein, upon bridgingof the crack from one material (e.g., the film 110, glass substrate 120or crack mitigating layer 130) to another material (e.g., the film 110,glass substrate 120 or crack mitigating layer 130). Crack deflection mayalso include causing a crack to propagate through the crack mitigatinglayer 130 instead of propagating into the film 110 and/or the glasssubstrate 120. In such instances, the crack mitigating layer 130 mayform a low toughness interface at the effective interface 140 thatfacilitates crack propagation through the crack mitigating layer insteadof into the glass substrate or film. This type of mechanism may bedescribed as deflecting the crack along the effective interface 140.

The following theoretical fracture mechanics analysis illustratesselected ways in which cracks may bridge or may be mitigated within alaminated article. FIG. 2 is a schematic illustrating the presence of acrack in a film disposed on a glass substrate and its possible bridgingor mitigation modes. The numbered elements in FIG. 2 are the glasssubstrate 10, the film 12 on top of a surface (unnumbered) of glasssubstrate 10, a two-sided deflection 14 into the interface between glasssubstrate 10 and film 12, an arrest 16 (which is a crack that started todevelop in film 12 but did not go completely through film 12), a“kinking” 18 (which is a crack that developed in the surface of film 12,but when it reached the surface of the glass substrate 10 it did notpenetrate into the glass substrate 12, but instead moves in a lateraldirection as indicated in FIG. 2 and then penetrates the surface of theglass substrate 10 at another position), a penetration crack 11 thatdeveloped in the film 12 and penetrated into the glass substrate 10, anda one-sided deflection 13. FIG. 2 also shows a graph of tension vs.compression 17 in the glass substrate 10 compared to zero axis 15. Asillustrated, upon application of external loading (in such cases,tensile loading is the most detrimental situation), the flaws in thefilm can be preferentially activated to form cracks prior to thedevelopment of cracks in the residually compressed or strengthened glasssubstrate. In the scenarios illustrated in FIG. 2, with continuedincrease of external loading, the cracks will bridge until theyencounter the glass substrate. When the cracks reach the surface ofglass substrate 10 the possible bridging modes of the crack, when itoriginates in the film are: (a) penetration into the glass substratewithout changing its path as represented by numeral 11; (b) deflectioninto one side along the interface between the film and the glasssubstrate as indicated by numeral 13; (c) deflection into two sidesalong the interface as indicated by numeral 14, (d) first deflectionalong the interface and then kinking into the glass substrate asindicated by numeral 18, or (e) crack arrest as indicated by numeral 16due to microscopic deformation mechanisms, for example, plasticity,nano-scale blunting, or nano-scale deflection at the crack tip. Cracksmay originate in the film and may bridge into the glass substrate. Theabove described bridging modes are also applicable where cracksoriginate in the glass substrate and bridge into the film, for examplewhere pre-existing cracks or flaws in the glass substrate may induce ornucleate cracks or flaws in the film, thus leading to crack growth orpropagation from the glass substrate into the film, resulting in crackbridging.

Crack penetration into the glass substrate and/or film reduces theaverage flexural strength of the laminated article and the glasssubstrate as compared to the average flexural strength of the glasssubstrate alone (i.e., without a film or a crack mitigating layer),while crack deflection, crack blunting or crack arrest (collectivelyreferred to herein as crack mitigation) helps retain the averageflexural strength of the article. Crack blunting and crack arrest can bedistinguished from one another. Crack blunting may comprise anincreasing crack tip radius, for example, through plastic deformation oryielding mechanisms. Crack arrest, on the other hand, could comprise anumber of different mechanisms such as, for example, encountering ahighly compressive stress at the crack tip, a reduction of the stressintensity factor at the crack tip resulting from the presence of alow-elastic modulus interlayer or a low-elastic modulus-to-high-elasticmodulus interface transition; nano-scale crack deflection or cracktortuosity as in some polycrystalline or composite materials, strainhardening at the crack tip and the like. The various modes of crackdeflection will be described herein.

Without being bound by theory, certain possible crack bridging paths canbe analyzed in the context of linear elastic fracture mechanics. In thefollowing paragraphs, one crack path is used as an example and thefracture mechanics concept is applied to the crack path to analyze theproblem and illustrate the requirements of material parameters to helpretain the average flexural strength performance of the article, for aparticular range of materials properties.

FIG. 3 below shows the illustration of the theoretical model framework.This is a simplified schematic view of the interface region between thefilm 12 and glass substrate 10. The terms μ₁, E₁, v₁, and μ₂, E₂, v₂,are shear modulus, Young's modulus, Poisson's ratio of glass substrateand film materials, Γ_(c) ^(Glass) and Γ_(c) ^(IT) are critical energyrelease rate of glass substrate and the interface between substrate andfilm, respectively.

The common parameters to characterize the elastic mismatch between thefilm and the substrate are Dundurs' parameters α and β, as defined below

$\begin{matrix}{\alpha = \frac{{\overset{\_}{E}}_{1} - {\overset{\_}{E}}_{2}}{{\overset{\_}{E}}_{1} + {\overset{\_}{E}}_{2}}} & (1)\end{matrix}$

where Ē=E/(1−v²) for plain strain and

$\begin{matrix}{\beta = {\frac{1}{2}\frac{{\mu_{1}\left( {1 - {2v_{2}}} \right)} - {\mu_{2}\left( {1 - {2v_{1}}} \right)}}{{\mu_{1}\left( {1 - v_{2}} \right)} + {\mu_{2}\left( {1 - v_{1}} \right)}}}} & (2)\end{matrix}$

It is worth pointing out that critical energy release rate is closelyrelated with the fracture toughness of the material through therelationship defined as

$\begin{matrix}{\Gamma = {\frac{1 - v^{2}}{E}K_{C}^{2}}} & (3)\end{matrix}$

Under the assumption that there is a pre-existing flaw in the film, upontensile loading the crack will extend vertically down as illustrated inFIG. 3. Right at the interface, the crack tends to deflect along theinterface if

$\begin{matrix}{\frac{G_{d}}{G_{p}} \geq \frac{\Gamma_{c}^{IT}}{\Gamma_{c}^{Glass}}} & (4)\end{matrix}$

and the crack will penetrate into the glass substrate if

$\begin{matrix}{\frac{G_{d}}{G_{p}} \geq \frac{\Gamma_{c}^{IT}}{\Gamma_{c}^{Glass}}} & (5)\end{matrix}$

where G_(d) and G_(p) and are the energy release rates of a deflectedcrack along the interface and a penetrated crack into the glasssubstrate, respectively. On the left hand side of equations (4) and (5),the ratio G_(d)/G_(p) is a strong function of elastic mismatch parameterα and weakly dependent on β; and on the right hand side, the toughnessratio Γ_(c) ^(IT)/γ_(c) ^(Glass) is a material parameter.

FIG. 4 graphically illustrates the trend of G_(d)/G_(p) as a function ofelastic mismatch α, reproduced from reference for doubly deflectedcracks. (Ming-Yuan, H. and J. W. Hutchinson, Crack deflection at aninterface between dissimilar elastic materials. International Journal ofSolids and Structures, 1989. 25(9): p. 1053-1067.).

It is evident that the ratio G_(d)/G_(p) is strongly dependent on α.Negative α means the film is stiffer than the glass substrate andpositive a means the film is softer than the glass substrate. Thetoughness ratio Γ_(c) ^(IT)/Γ_(c) ^(Glass) which is independent of α isa horizontal line in FIG. 4. If criterion (4) is satisfied, in FIG. 4,at the region above the horizontal line, the crack tends to deflectalong the interface which may be beneficial for the retention of asubstrate's average flexural strength. On the other hand, if thecriterion (5) is satisfied, in FIG. 4, at the region below thehorizontal line, the crack tends to penetrate into glass substrate whichleads to degradation of the average flexural strength of the article,particularly those articles utilizing strengthened or strong glasssubstrates as described elsewhere herein.

With the above concept, in the following, an indium-tin-oxide (ITO) filmis utilized as an illustrative example. For glass substrate, E₁=72 GPa,v₁=0.22, and K_(1c)=0.7 MPa m^(1/2); for ITO, E₂=99.8 GPa, v₂=0.25.(Zeng, K., et al., Investigation of mechanical properties of transparentconducting oxide thin films. Thin Solid Films, 2003. 443(1-2): p.60-65.). The interfacial toughness between the ITO film and glasssubstrate can be approximately Γ_(in)=J/m², depending on depositionconditions. (Cotterell, B. and Z. Chen, Buckling and cracking of thinfilms on compliant substrates under compression. International Journalof Fracture, 2000. 104(2): p. 169-179.). This will give the elasticmismatch α=−0.17 and Γ_(c) ^(IT)/Γ_(c) ^(Glass)=0.77. These values areplotted in FIG. 4. This fracture analysis predicts that the crackpenetration into the glass substrate for the ITO film will be favored,which leads to degradation of the average flexural strength of theglass, particularly glass that is strengthened or strong. This isbelieved to be one of the potential underlying mechanisms observed withvarious indium-tin-oxide or other transparent conductive oxide filmsthat are disposed on glass substrates, including strengthened or strongglass substrates. As shown in FIG. 4, one way to mitigate thedegradation of the average flexural strength can be to selectappropriate materials to change the elastic mismatch α (choice 1) or toadjust the interfacial toughness (choice 2).

The theoretical analysis outlined above suggests that a crack mitigatinglayer 130 can be used to better retain the article strength.Specifically, the insertion of a crack mitigating layer between a glasssubstrate 120 and a film 110 makes crack mitigation, as defined herein,a more preferred path and thus the article is better able to retain itsstrength. In some embodiments, the crack mitigating layer 130facilitates crack deflection, as will be described in greater detailherein.

Glass Substrate

Referring to FIG. 1, the article 100 includes a glass substrate 120,which may be strengthened or strong, as described herein, havingopposing major surfaces 122, 124, a film 110 disposed on a at least oneopposing major surface (122 or 124) and a crack mitigating layer 130disposed between the film 110 and the glass substrate 120. In one ormore alternative embodiments, the crack mitigating layer 130 and thefilm 110 may be disposed on the minor surface(s) of the glass substratein addition to or instead of being disposed on at least one majorsurface (122 or 124). As used herein, the glass substrate 120 may besubstantially planar sheets, although other embodiments may utilize acurved or otherwise shaped or sculpted glass substrate. The glasssubstrate 120 may be substantially clear, transparent and free fromlight scattering. The glass substrate may have a refractive index in therange from about 1.45 to about 1.55. In one or more embodiments, theglass substrate 120 may be strengthened or characterized as strong, aswill be described in greater detail herein. The glass substrate 120 maybe relatively pristine and flaw-free (for example, having a low numberof surface flaws or an average surface flaw size less than about 1micron) before such strengthening. Where strengthened or strong glasssubstrates 120 are utilized, such substrates may be characterized ashaving a high average flexural strength (when compared to glasssubstrates that are not strengthened or strong) or high surfacestrain-to-failure (when compared to glass substrates that are notstrengthened or strong) on one or more major opposing surfaces of suchsubstrates.

Additionally or alternatively, the thickness of the glass substrate 120may vary along one or more of its dimensions for aesthetic and/orfunctional reasons. For example, the edges of the glass substrate 120may be thicker as compared to more central regions of the glasssubstrate 120. The length, width and thickness dimensions of the glasssubstrate 120 may also vary according to the article 100 application oruse.

The glass substrate 120 according to one or more embodiments includes anaverage flexural strength that may be measured before and after theglass substrate 120 is combined with the film 110, crack mitigatinglayer 130 and/or other films or layers. In one or more embodimentsdescribed herein, the article 100 retains its average flexural strengthafter the combination of the glass substrate 120 with the film 110,crack mitigating layer 130 and/or other films, layers or materials, whencompared to the average flexural strength of the glass substrate 120before such combination. In other words, the average flexural strengthof the article 100 is substantially the same before and after the film110, crack mitigating layer 130 and/or other films or layers aredisposed on the glass substrate 120. In one or more embodiments, thearticle 100 has an average flexural strength that is significantlygreater than the average flexural strength of a similar article thatdoes not include the crack mitigating layer 130 (e.g. higher strengththan an article that comprises film 110 and glass substrate 120 indirect contact, without an intervening crack mitigating layer).

In accordance with one or more embodiments, the glass substrate 120 hasan average strain-to-failure that may be measured before and after theglass substrate 120 is combined with the film 110, crack mitigatinglayer 130 and/or other films or layers. The term “averagestrain-to-failure” refers to the strain at which cracks propagatewithout application of additional load, typically leading tocatastrophic failure in a given material, layer or film and, perhapseven bridge to another material, layer, or film, as defined herein.Average strain-to-failure may be measured using, for example,ball-on-ring testing. Without being bound by theory, the averagestrain-to-failure may be directly correlated to the average flexuralstrength using appropriate mathematical conversions. In specificembodiments, the glass substrate 120, which may be strengthened orstrong as described herein, has an average strain-to-failure that is0.5% or greater, 0.6% or greater, 0.7% or greater, 0.8% or greater, 0.9%or greater, 1% or greater, 1.1% or greater, 1.2% or greater, 1.3% orgreater, 1.4% or greater 1.5% or greater or even 2% or greater. Inspecific embodiments, the glass substrate has an averagestrain-to-failure of 1.2%, 1.4%, 1.6%, 1.8%, 2.2%, 2.4%, 2.6%, 2.8% or3% or greater. The average strain-to-failure of the film 110 may be lessthan the average strain-to-failure of the glass substrate 120 and/or theaverage strain-to-failure of the crack mitigating layer 130. Withoutbeing bound by theory, it is believed that the average strain-to-failureof a glass substrate or any other material is dependent on the surfacequality of such material. With respect to glass substrates, the averagestrain-to-failure of a specific glass substrate is dependent on theconditions of ion exchange or strengthening process utilized in additionto or instead of the surface quality of the glass substrate.

In one or more embodiments, the glass substrate 120 retains its averagestrain-to-failure after combination with the film 110, crack mitigatinglayer 130 and/or other films or layers. In other words, the averagestrain-to-failure of the glass substrate 120 is substantially the samebefore and after the film 110, crack mitigating layer 130 and/or otherfilms or layers are disposed on the glass substrate 120. In one or moreembodiments, the article 100 has an average strain-to-failure that issignificantly greater than the average strain-to-failure of a similararticle that does not include the crack mitigating layer 130 (e.g.higher strain-to-failure than an article that comprises film 110 andglass substrate 120 in direct contact, without an intervening crackmitigating layer). For example, the article 100 may exhibit an averagestrain-to-failure that is at least 10% higher, 25% higher, 50% higher,100% higher, 200% higher or 300% higher than the averagestrain-to-failure of a similar article that does not include the crackmitigating layer 130.

The glass substrate 120 may be provided using a variety of differentprocesses. For instance, example glass substrate forming methods includefloat glass processes and down-draw processes such as fusion draw andslot draw.

In the float glass process, a glass substrate that may be characterizedby smooth surfaces and uniform thickness is made by floating moltenglass on a bed of molten metal, typically tin. In an example process,molten glass that is fed onto the surface of the molten tin bed forms afloating glass ribbon. As the glass ribbon flows along the tin bath, thetemperature is gradually decreased until the glass ribbon solidifiesinto a solid glass substrate that can be lifted from the tin ontorollers. Once off the bath, the glass substrate can be cooled furtherand annealed to reduce internal stress.

Down-draw processes produce glass substrates having a uniform thicknessthat may possess relatively pristine surfaces. Because the averageflexural strength of the glass substrate is controlled by the frequency,amount and/or size of surface flaws, a pristine surface that has hadminimal contact has a higher initial strength. When this high strengthglass substrate is then further strengthened (e.g., chemically), theresultant strength can be higher than that of a glass substrate with asurface that has been lapped and polished. Down-drawn glass substratesmay be drawn to a thickness of less than about 2 mm. In addition, downdrawn glass substrates may have a very flat, smooth surface that can beused in its final application without costly grinding and polishing.

The fusion draw process, for example, uses a drawing tank that has achannel for accepting molten glass raw material. The channel has weirsthat are open at the top along the length of the channel on both sidesof the channel. When the channel fills with molten material, the moltenglass overflows the weirs. Due to gravity, the molten glass flows downthe outside surfaces of the drawing tank as two flowing glass films.These outside surfaces of the drawing tank extend down and inwardly sothat they join at an edge below the drawing tank. The two flowing glassfilms join at this edge to fuse and form a single flowing glasssubstrate. The fusion draw method offers the advantage that, because thetwo glass films flowing over the channel fuse together, neither of theoutside surfaces of the resulting glass substrate comes in contact withany part of the apparatus. Thus, the surface properties of the fusiondrawn glass substrate are not affected by such contact.

The slot draw process is distinct from the fusion draw method. In slotdraw processes, the molten raw material glass is provided to a drawingtank. The bottom of the drawing tank has an open slot with a nozzle thatextends the length of the slot. The molten glass flows through theslot/nozzle and is drawn downward as a continuous substrate and into anannealing region.

Once formed, glass substrates may be strengthened to form strengthenedglass substrates. As used herein, the term “strengthened glasssubstrate” may refer to a glass substrate that has been chemicallystrengthened, for example through ion-exchange of larger ions forsmaller ions in the surface of the glass substrate. However, otherstrengthening methods known in the art, such as thermal tempering, maybe utilized to form strengthened glass substrates. As will be described,strengthened glass substrates may include a glass substrate having asurface compressive stress in its surface that aids in the strengthpreservation of the glass substrate. Strong glass substrates are alsowithin the scope of this disclosure and include glass substrates thatmay not have undergone a specific strengthening process, and may nothave a surface compressive stress, but are nevertheless strong. Suchstrong glass substrates articles may be defined as glass sheet articlesor glass substrates having an average strain-to-failure greater thanabout 0.5%, 0.7%, 1%, 1.5%, or even greater than 2%. Such strong glasssubstrates can be made, for example, by protecting the pristine glasssurfaces after melting and forming the glass substrate. An example ofsuch protection occurs in a fusion draw method, where the surfaces ofthe glass films do not come into contact with any part of the apparatusor other surface after forming. The glass substrates formed from afusion draw method derive their strength from their pristine surfacequality. A pristine surface quality can also be achieved through etchingor polishing and subsequent protection of glass substrate surfaces, andother methods known in the art. In one or more embodiments, bothstrengthened glass substrates and the strong glass substrates maycomprise glass sheet articles having an average strain-to-failuregreater than about 0.5%, 0.7%, 1%, 1.5%, or even greater than 2%, forexample when measured using ring-on-ring or ball-on-ring flexuraltesting.

As mentioned above, the glass substrates described herein may bechemically strengthened by an ion exchange process to provide astrengthened glass substrate 120. The glass substrate may also bestrengthened by other methods known in the art, such as thermaltempering. In the ion-exchange process, typically by immersion of theglass substrate into a molten salt bath for a predetermined period oftime, ions at or near the surface(s) of the glass substrate areexchanged for larger metal ions from the salt bath. In one embodiment,the temperature of the molten salt bath is about 350° C. to 450° C. andthe predetermined time period is about two to about eight hours. Theincorporation of the larger ions into the glass substrate strengthensthe glass substrate by creating a compressive stress in a near surfaceregion or in regions at and adjacent to the surface(s) of the glasssubstrate. A corresponding tensile stress is induced within a centralregion or regions at a distance from the surface(s) of the glasssubstrate to balance the compressive stress. Glass substrates utilizingthis strengthening process may be described more specifically aschemically-strengthened glass substrates 120 or ion-exchanged glasssubstrates 120. Glass substrates that are not strengthened may bereferred to herein as non-strengthened glass substrates.

In one example, sodium ions in a strengthened glass substrate 120 arereplaced by potassium ions from the molten bath, such as a potassiumnitrate salt bath, though other alkali metal ions having larger atomicradii, such as rubidium or cesium, can replace smaller alkali metal ionsin the glass. According to particular embodiments, smaller alkali metalions in the glass can be replaced by Ag⁺ ions. Similarly, other alkalimetal salts such as, but not limited to, sulfates, phosphates, halides,and the like may be used in the ion exchange process.

The replacement of smaller ions by larger ions at a temperature belowthat at which the glass network can relax produces a distribution ofions across the surface(s) of the strengthened glass substrate 120 thatresults in a stress profile. The larger volume of the incoming ionproduces a compressive stress (CS) on the surface and tension (centraltension, or CT) in the center of the strengthened glass substrate 120.Depth of exchange may be described as the depth within the strengthenedglass substrate 120 (i.e., the distance from a surface of the glasssubstrate to a central region of the glass substrate), at which ionexchange facilitated by the ion exchange process takes place.

In one embodiment, a strengthened glass substrate 120 can have a surfacecompressive stress of 300 MPa or greater, e.g., 400 MPa or greater, 450MPa or greater, 500 MPa or greater, 550 MPa or greater, 600 MPa orgreater, 650 MPa or greater, 700 MPa or greater, 750 MPa or greater or800 MPa or greater. The strengthened glass substrate 120 may have acompressive depth of layer 15 μm or greater, 20 μm or greater (e.g., 25μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or greater) and/or a centraltension of 10 MPa or greater, 20 MPa or greater, 30 MPa or greater, 40MPa or greater (e.g., 42 MPa, 45 MPa, or 50 MPa or greater) but lessthan 100 MPa (e.g., 95, 90, 85, 80, 75, 70, 65, 60, 55 MPa or less). Inone or more specific embodiments, the strengthened glass substrate 120has one or more of the following: a surface compressive stress greaterthan 500 MPa, a depth of compressive layer greater than 15 μm, and acentral tension greater than 18 MPa.

Without being bound by theory, it is believed that strengthened glasssubstrates 120 with a surface compressive stress greater than 500 MPaand a compressive depth of layer greater than about 15 μm typically havegreater strain-to-failure than non-strengthened glass substrates (or, inother words, glass substrates that have not been ion exchanged orotherwise strengthened). In some embodiments, the benefits of one ormore embodiments described herein may not be as prominent withnon-strengthened or weakly strengthened types of glass substrates thatdo not meet these levels of surface compressive stress or compressivedepth of layer, because of the presence of handling or common glasssurface damage events in many typical applications. However, asmentioned previously, in other specific applications where the glasssubstrate surfaces can be adequately protected from scratches or surfacedamage (for example by a protective coating or other layers), strongglass substrates with a relatively high strain-to-failure can also becreated through forming and protection of a pristine glass surfacequality, using methods such as the fusion forming method. In thesealternate applications, the benefits of one or more embodimentsdescribed herein can be similarly realized.

Example ion-exchangeable glasses that may be used in the strengthenedglass substrate 120 may include alkali aluminosilicate glasscompositions or alkali aluminoborosilicate glass compositions, thoughother glass compositions are contemplated. As used herein, “ionexchangeable” means that a glass substrate is capable of exchangingcations located at or near the surface of the glass substrate withcations of the same valence that are either larger or smaller in size.One example glass composition comprises SiO₂, B₂O₃ and Na₂O, where(SiO₂+B₂O₃)≧66 mol. %, and Na₂O≧9 mol. %. In an embodiment, the glasssubstrate 120 includes a glass composition with at least 6 wt. %aluminum oxide. In a further embodiment, a glass substrate 120 includesa glass composition with one or more alkaline earth oxides, such that acontent of alkaline earth oxides is at least 5 wt. %. Suitable glasscompositions, in some embodiments, further comprise at least one of K₂O,MgO, and CaO. In a particular embodiment, the glass compositions used inthe glass substrate 120 can comprise 61-75 mol. % SiO₂; 7-15 mol. %Al₂O₃; 0-12 mol. % B₂O₃; 9-21 mol. % Na₂O; 0-4 mol. % K₂O; 0-7 mol. %MgO; and 0-3 mol. % CaO.

A further example glass composition suitable for the glass substrate120, which may optionally be strengthened or strong, comprises: 60-70mol. % SiO₂; 6-14 mol. % Al₂O₃; 0-15 mol. % B₂O₃; 0-15 mol. % Li₂O; 0-20mol. % Na₂O; 0-10 mol. % K₂O; 0-8 mol. % MgO; 0-10 mol. % CaO; 0-5 mol.% ZrO₂; 0-1 mol. % SnO₂; 0-1 mol. % CeO₂; less than 50 ppm As₂O₃; andless than 50 ppm Sb₂O₃; where 12 mol. %≦(Li₂O+Na₂O+K₂O)≦20 mol. % and 0mol. %≦(MgO+CaO)≦10 mol. %.

A still further example glass composition suitable for the glasssubstrate 120, which may optionally be strengthened or strong,comprises: 63.5-66.5 mol. % SiO₂; 8-12 mol. % Al₂O₃; 0-3 mol. % B₂O₃;0-5 mol. % Li₂O; 8-18 mol. % Na₂O; 0-5 mol. % K₂O; 1-7 mol. % MgO; 0-2.5mol. % CaO; 0-3 mol. % ZrO₂; 0.05-0.25 mol. % SnO₂; 0.05-0.5 mol. %CeO₂; less than 50 ppm As₂O₃; and less than 50 ppm Sb₂O₃; where 14 mol.%≦(Li₂O+Na₂O+K₂O)≦18 mol. % and 2 mol. %≦(MgO+CaO)≦7 mol. %.

In a particular embodiment, an alkali aluminosilicate glass compositionsuitable for the glass substrate 120, which may optionally bestrengthened or strong, comprises alumina, at least one alkali metaland, in some embodiments, greater than 50 mol. % SiO₂, in otherembodiments at least 58 mol. % SiO₂, and in still other embodiments atleast 60 mol. % SiO₂, wherein the ratio

${\frac{{{Al}_{2}O_{3}} + {B_{2}O_{3}}}{\sum{modifiers}} > 1},$

where in the ratio the components are expressed in mol. % and themodifiers are alkali metal oxides. This glass composition, in particularembodiments, comprises: 58-72 mol. % SiO₂; 9-17 mol. % Al₂O₃; 2-12 mol.% B₂O₃; 8-16 mol. % Na₂O; and 0-4 mol. % K₂O, wherein the ratio

$\frac{{{Al}_{2}O_{3}} + {B_{2}O_{3}}}{\sum{modifiers}} > 1.$

In still another embodiment, the glass substrate, which may optionallybe strengthened or strong, may include an alkali aluminosilicate glasscomposition comprising: 64-68 mol. % SiO₂; 12-16 mol. % Na₂O; 8-12 mol.% Al₂O₃; 0-3 mol. % B₂O₃; 2-5 mol. % K₂O; 4-6 mol. % MgO; and 0-5 mol. %CaO, wherein: 66 mol. %≦SiO₂+B₂O₃+CaO≦69 mol. %;Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>10 mol. %; 5 mol. %≦MgO+CaO+SrO≦8 mol. %;(Na₂O+B₂O₃)—Al₂O₃≦2 mol. %; 2 mol. %≦Na₂O—Al₂O₃≦6 mol. %; and 4 mol.%≦(Na₂O+K₂O)—Al₂O₃≦10 mol. %.

In some embodiments, the glass substrate 120, which may optionally bestrengthened or strong, may comprise an alkali silicate glasscomposition comprising: 2 mol % or more of Al₂O₃ and/or ZrO₂, or 4 mol %or more of Al₂O₃ and/or ZrO₂.

In some embodiments, the glass substrate used in the glass substrate 120may be batched with 0-2 mol % of at least one fining agent selected froma group that includes Na₂SO₄, NaCl, NaF, NaBr, K₂SO₄, KCl, KF, KBr, andSnO₂.

The glass substrate 120 according to one or more embodiments can have athickness ranging from about 50 μm to 5 mm. Example glass substrate 120thicknesses range from 100 μm to 500 μm, e.g., 100, 200, 300, 400 or 500μm. Further example glass substrate 120 thicknesses range from 500 μm to1000 μm, e.g., 500, 600, 700, 800, 900 or 1000 μm. The glass substrate120 may have a thickness greater than 1 mm, e.g., about 2, 3, 4, or 5mm. In one or more specific embodiments, the glass substrate 120 mayhave a thickness of 2 mm or less or less than 1 mm. The glass substrate120 may be acid polished or otherwise treated to remove or reduce theeffect of surface flaws.

Film

The article 100 includes a film 110 disposed on a surface of the glasssubstrate 120 and specifically on the crack mitigating layer 130. Thefilm 110 may be disposed on one or both major surfaces 122, 124 of theglass substrate 120. In one or more embodiments, the film 110 may bedisposed on one or more minor surfaces (not shown) of the glasssubstrate 120 in addition to or instead of being disposed on one or bothmajor surfaces 122, 124. In one or more embodiments, the film 110 isfree of macroscopic scratches or defects that are easily visible to theeye. The film 110 forms the effective interface 140 with the glasssubstrate 120.

In one or more embodiments, the film may lower the average flexuralstrength of articles incorporating such films and glass substrate,through the mechanisms described herein. In one or more embodiments,such mechanisms include instances in which the film may lower theaverage flexural strength of the article because crack(s) developing insuch film bridge into the glass substrate. In other embodiments, themechanisms include instances in which the film may lower the averageflexural strength of the article because cracks developing in the glasssubstrates bridge into the film. The film of one or more embodiments mayexhibit a strain-to-failure of 2% or less or a strain-to-failure that isless than the strain to failure of the glass substrates describedherein. Films including any of these attributes may be characterized asbrittle.

In accordance with one or more embodiments, the film 110 may have astrain-to-failure (or crack onset strain level) that is lower than thestrain-to-failure of the glass substrate 120. For example, the film 110may have strain-to-failure of about 2% or less, about 1.8% or less,about 1.6% or less, about 1.5% or less, about 1.4% or less, about 1.2%or less, about 1% or less, about 0.8% or less, about 0.6% or less, about0.5% or less, about 0.4% or less or about 0.2% or less. In someembodiments, the strain-to-failure of the film 110 may be lower thanthat the strain-to-failure of the strengthened glass substrates 120 thathave a surface compressive stress greater than 500 MPa and a compressivedepth of layer greater than about 15 μm. In one or more embodiments, thefilm 110 may have a strain-to-failure that is at least 0.1% lower orless, or in some cases, at least 0.5% lower or less than thestrain-to-failure of the glass substrate 120. In one or moreembodiments, the film 110 may have a strain-to-failure that is at leastabout 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.55%, 0.6%, 0.65%,0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 0.95% or 1% lower or less than thestrain-to-failure of the glass substrate 120. These strain-to-failurevalues can be measured, for example, using ball-on-ring flexural testmethods combined with optional microscopic or high-speed-cameraanalysis. In some cases the onset of film cracking may be measured byanalyzing the electrical resistivity of a conducting film. These variousanalyses can be performed during the application of load or stress, orin some cases after the application of load or stress.

Exemplary films 110 may have an elastic modulus of at least 25 GPaand/or a hardness of at least 1.75 GPa, although some combinationsoutside of this range are possible. In some embodiments the film 110 mayhave an elastic modulus 50 GPa or greater or even 70 GPa or greater. Forexample, the film elastic modulus may be 55 GPa, 60 GPa, 65 GPa, 75 GPa,80 GPa, 85 GPa or more. In one or more embodiments, the film 110 mayhave a hardness greater than 3.0 GPa. For example, the film 110 may havea hardness of 5 GPa, 5.5 GPa, 6 GPa, 6.5 GPa, 7 GPa, 7.5 GPa, 8 GPa, 8.5GPa, 9 GPa, 9.5 GPa, 10 GPa or greater. These elastic modulus andhardness values can be measured for such films 110 using known diamondnano-indentation methods that are commonly used for determining theelastic modulus and hardness of films. Exemplary diamondnano-indentation methods may utilize a Berkovich diamond indenter.

The films 110 described herein may also exhibit a fracture toughnessless than about 10 MPa·m^(1/2), or in some cases less than 5MPa·m^(1/2), or in some cases less than 1 MPa·m^(1/2). For example, thefilm may have a fracture toughness of 4.5 MPa·m^(1/2), 4 MPa·m^(1/2),3.5 MPa·m^(1/2), 3 MPa·m^(1/2), 2.5 MPa·m^(1/2), 2 MPa·m^(1/2), 1.5MPa·m^(1/2), 1.4 MPa·m^(1/2), 1.3 MPa·m^(1/2), 1.2 MPa·m^(1/2), 1.1MPa·m^(1/2), 0.9 MPa·m^(1/2), 0.8 MPa·m^(1/2), 0.7 MPa·m^(1/2), 0.6MPa·m^(1/2), 0.5 MPa·m^(1/2), 0.4 MPa·m^(1/2), 0.3 MPa·m^(1/2), 0.2MPa·m^(1/2), 0.1 MPa·m^(1/2) or less.

The films 110 described herein may also have a critical strain energyrelease rate (G_(IC)=K_(IC) ²/E) that is less than about 0.1 kJ/m², orin some cases less than 0.01 kJ/m². In one or more embodiments, the film110 may have a critical strain energy release rate of 0.09 kJ/m², 0.08kJ/m², 0.07 kJ/m², 0.06 kJ/m², 0.05 kJ/m², 0.04 kJ/m², 0.03 kJ/m², 0.02kJ/m², 0.0075 kJ/m², 0.005 kJ/m², 0.0025 kJ/m² or less.

In one or more embodiments, the film 110 may include a plurality oflayers. In one or more embodiments, each of the layers of the film maybe characterized as brittle based on one or more of the layer's impacton the average flexural strength of the article and/or the layer'sstrain-to-failure, fracture toughness, or critical strain energy releaserate values, as otherwise described herein. In one variant, the layersof the film 110 need not have identical properties such as elasticmodulus and/or fracture toughness. In another variant, the layers of thefilm 110 may include different materials from one another.

The compositions or material(s) of the film 110 are not particularlylimited. Some non-limiting examples of film 110 materials include oxidessuch as SiO₂, Al₂O₃, TiO₂, Nb₂O₅, Ta₂O₅; oxynitrides such asSiO_(x)N_(y), SiAl_(x)O_(y)N_(z), and AlO_(x)N_(y); nitrides such asSiN_(x), AlN_(x), cubic boron nitride, and TiN_(x); carbides such asSiC, TiC, and WC; combinations of the above such as oxycarbides andoxy-carbo-nitrides (for example, SiC_(x)O_(y) and SiC_(x)O_(y)N_(z));semiconductor materials such as Si and Ge; transparent conductors suchas indium-tin-oxide, tin oxide, fluorinated tin oxide, aluminum zincoxide, or zinc oxide; carbon nanotube or graphene-doped oxides; silveror other metal-doped oxides, highly siliceous polymers such as highlycured siloxanes and silsesquioxanes; diamond or diamond-like-carbonmaterials; or selected metal films which can exhibit a fracturebehavior.

The film 110 can be disposed on the glass substrate 120 by vacuumdeposition techniques, for example, chemical vapor deposition (e.g.,plasma enhanced chemical vapor deposition, atmospheric pressure chemicalvapor deposition, or plasma-enhanced atmospheric pressure chemical vapordeposition), physical vapor deposition (e.g., reactive or nonreactivesputtering or laser ablation), thermal, resistive, or e-beamevaporation, or atomic layer deposition. The film 110 may also bedisposed on one or more surfaces 122, 124 of the glass substrate 120using liquid-based techniques, for example sol-gel coating or polymercoating methods, for example spin, spray, slot draw, slide, wire-woundrod, blade/knife, air knife, curtain, gravure, and roller coating amongothers. In some embodiments it may be desirable to use adhesionpromoters, such as silane-based materials, between the film 110 and theglass substrate 120, between the glass substrate 120 and crackmitigating layer 130, between the layers (if any) of the crackmitigating layer 130, between the layers (if any) of the film 110 and/orbetween the film 110 and the crack mitigating layer 130. In one or morealternative embodiments, the film 110 may be disposed on the glasssubstrate 120 as a transfer layer.

The film 110 thickness can vary depending on the intended use of thearticle 100. In one embodiment the film 110 thickness may be in theranges from about 0.005 μm to about 0.5 μm or from about 0.01 μm toabout 20 μm. In another embodiment, the film 110 may have a thickness inthe range from about 0.05 μm to about 10 μm, from about 0.05 μm to about0.5 μm, from about 0.01 μm to about 0.15 μm or from about 0.015 μm toabout 0.2 μm.

In some embodiments it may be advantageous to include a material in thefilm 110 that has either:

(1) a refractive index that is similar to the refractive index of eitherthe glass substrate 120, the crack mitigating layer 130 and/or otherfilms or layers in order to minimize optical interference effects;

(2) a refractive index (real and/or imaginary components) that is tunedto achieve anti-reflective interference effects; and/or

(3) a refractive index (real and/or imaginary components) that is tunedto achieve wavelength-selective reflective or wavelength-selectiveabsorptive effects, such as to achieve UV or IR blocking or reflection,or to achieve coloring/tinting effects.

In one or more embodiments, the film 110 may have a refractive indexthat is greater than the refractive index of the glass substrate 120and/or greater than the refractive index of the crack mitigating layer130. In one or more embodiments, the film may have a refractive index inthe range from about 1.7 to about 2.2, or in the range from about 1.4 toabout 1.6, or in the range from about 1.6 to about 1.9.

The film 110 may also serve multiple functions, or be integrated withadditional film(s) or layers as described herein that serve otherfunctions than the film 110 or even the same function(s) as the film110. The film 110 may include UV or IR light reflecting or absorbinglayers, anti-reflection layers, anti-glare layers, dirt-resistantlayers, self-cleaning layers, scratch-resistant layers, barrier layers,passivation layers, hermetic layers, diffusion-blocking layers,fingerprint-resistant layers, and the like. Further, the film 110 mayinclude conducting or semi-conducting layers, thin film transistorlayers, EMI shielding layers, breakage sensors, alarm sensors,electrochromic materials, photochromic materials, touch sensing layers,or information display layers. The film 110 and/or any of the foregoinglayers may include colorants or tint. When information display layersare integrated into the article 100, the article 100 may form part of atouch-sensitive display, a transparent display, or a heads-up display.It may be desirable that the film 110 performs an interference function,which selectively transmits, reflects, or absorbs different wavelengthsor colors of light. For example, the films 110 may selectively reflect atargeted wavelength in a heads-up display application.

Functional properties of the film 110 may include optical properties,electrical properties and/or mechanical properties, such as hardness,elastic modulus, strain-to-failure, abrasion resistance, mechanicaldurability, coefficient of friction, electrical conductivity, electricalresistivity, electron mobility, electron or hole carrier doping, opticalrefractive index, density, opacity, transparency, reflectivity,absorptivity, transmissivity and the like. These functional propertiesare substantially maintained or even improved after the film 110 iscombined with the glass substrate 120, crack mitigating layer 130 and/orother films included in the article 100.

Crack Mitigating Layer

As described herein, the crack mitigating layer provides a moderateadhesion energy at the effective interface 140. The crack mitigatinglayer 130 provides a moderate adhesion energy by forming a low toughnesslayer at the effective interface that facilitates crack deflection intothe crack mitigating layer instead of the film 110 or glass substrate120. The crack mitigating layer 130 may also provide a moderate adhesionenergy by forming a low toughness interface. The low toughness interfaceis characterized by delamination of the crack mitigating layer 130 fromthe glass substrate 120 or film 110 upon application of a specifiedload. This delamination causes cracks to deflect along either the firstinterface 150 or the second interface 160. Cracks may also deflect alonga combination of the first and second interfaces 150 and 160, forexample following a path which may cross over from one interface to theother.

In one or more embodiments, crack mitigating layer 130 provides moderateadhesion by modifying the effective adhesion energy at the effectiveinterface 140 between the glass substrate 120 and the film 110. In oneor more specific embodiments, one or both of the first interface 150 andthe second interface 160 exhibit the effective adhesion energy. In oneor more embodiments, the effective adhesion energy may be about 5 J/m²or less, about 4.5 J/m² or less, about 4 J/m² or less, about 3.5 J/m² orless, about 3 J/m² or less, about 2.5 J/m² or less, about 2 J/m² orless, about 1.5 J/m² or less, about 1 J/m² or less or about 0.85 J/m² orless. The lower limit of the effective adhesion energy may be about 0.1J/m² or about 0.01 J/m². In one or more embodiments, the effectiveadhesion energy at one or more of the first interface and the secondinterface may be in the range from about 0.85 J/m² to about 3.85 J/m²,from about 0.85 J/m² to about 3 J/m², from about 0.85 J/m² to about 2J/m², and from about 0.85 J/m² to about 1 J/m². The effective adhesionenergy at one or more of the first interface and the second interfacecan also be between about 0.1 J/m² and about 0.85 J/m², or between about0.3 J/m² and about 0.7 J/m². According to some embodiments, theeffective adhesion energy at one or more of the first interface and thesecond interface remains substantially constant, or within a targetrange such as from 0.1 J/m² and about 0.85 J/m², from ambienttemperature up to about 600° C. In some embodiments, the effectiveadhesion energy at one or more of the interfaces is at least 25% lessthan the average cohesive adhesion energy of the glass substrate fromambient temperature up to about 600° C.

In embodiments in which the effective interface, 140, the firstinterface 150 and/or the second interface 160 exhibits moderateadhesion, at least a portion of the crack mitigating layer may separatefrom the glass substrate and/or the film during a loading process thatcauses crack growth and/or crack formation in the film and/or the crackmitigating layer. When at least a portion of the crack mitigating layerseparates from the glass substrate 120 and/or the film 110, suchseparation may include a reduced adhesion or no adhesion between thecrack mitigating layer and the glass substrate 120 and/or film 110 fromwhich the crack mitigating layer separates. In other embodiments, whenonly a portion of the crack mitigating layer separates, such separatedportion may be surrounded completely or at least partially by portionsof the crack mitigating layer still adhered to the glass substrate 120and/or film 110. In one or more embodiments, at least a portion of thecrack mitigating layer 130 may separate from one of the film 110 or theglass substrate 120 when the laminated article is strained at aspecified strain level during such loading. In one or more embodiments,the strain level may be between the first average strain-to-failure ofthe glass substrate 120 and the average strain-to-failure of the film110.

In one or more specific embodiments, at least a portion of the crackmitigating layer 130 separates from the film 110 when a crackoriginating in the film 110 bridges into the crack mitigating layer 130(or crosses the second interface 160). In a particular embodiment, atleast a portion of the crack mitigating layer 130 separates from thefilm 110 as an adhesive failure 190 at the interface 160 (see FIG. 9B)when a crack originating in the film 110 bridges into the crackmitigating layer 130. In other embodiments, at least a portion of thecrack mitigating layer 130 separates from the glass substrate 120 when acrack originating in the glass substrate 120 bridges into the crackmitigating layer 130 (or crosses the first interface 150). In anotherparticular embodiment, at least a portion of the crack mitigating layer130 separates from the glass substrate 120 as an adhesive failure 190 atthe interface 150 (see FIG. 9B) when a crack originating in the glasssubstrate 120 bridges into the crack mitigating layer 130. As usedherein, the term “adhesive failure” relates to crack propagationsubstantially confined to one or more of the interfaces 150 and 160between the crack mitigating layer 130, the film 110 and the glasssubstrate 120.

The crack mitigating layer does not separate and remains adhered to theglass substrate 120 and the film 110 at load levels that do not causecrack growth and/or crack formation (i.e., at average strain-to-failurelevels less than the average strain-to-failure of the glass substrateand less than the average strain-to-failure of the film). Without beingbound by theory, delamination or partial delamination of the crackmitigating layer 130 reduces the stress concentrations in the glasssubstrate 120. Accordingly, it is believed that a reduction in stressconcentrations in the glass substrate 120 causes an increase in the loador strain level that is required for the glass substrate 120 (andultimately the laminated article 100) to fail. In this manner, the crackmitigating layer 130 prevents a decrease or increases the averageflexural strength of the laminated article, as compared to laminatedarticles without the crack mitigating layer.

The material and thickness of the crack mitigating layer 130 can be usedto control the effective adhesion energy between glass substrate 120 andthe film 110. In general, the adhesion energy between two surfaces isgiven by (“A theory for the estimation of surface and interfacialenergies. I. derivation and application to interfacial tension”, L. A.Girifalco and R. J. Good, J. Phys. Chem., V 61, p904):

W=γ ₁+γ₂−γ₁₂  (6)

where, γ₁, γ₂ and γ₁₂ are the surface energies of surface 1, surface 2and the interfacial energy of surface 1 and 2 respectively. Theindividual surface energies are usually a combination of two terms; adispersion component γ^(d), and a polar component γ^(p)

γ=γ^(d)+γ^(p)  (7)

When the adhesion is mostly due to London dispersion forces (γ^(d)) andpolar forces for example hydrogen bonding (γ^(p)), the interfacialenergy could be given by (Girifalco and R. J. Good, as mentioned above):

γ₁₂=γ₁+γ₂−2√{square root over (γ₁ ^(d)γ₂ ^(d))}−2√{square root over (γ₁^(p)γ₂ ^(p))}  (8)

After substituting (3) in (1), the energy of adhesion could beapproximately calculated as:

W˜2┌√{square root over (γ₁ ^(d)γ₂ ^(d))}+√{square root over (γ₁ ^(p)γ₂^(p))}]  (9)

In the above equation (9), only van der Waal (and/or hydrogen bonding)components of adhesion energies are considered. These includepolar-polar interaction (Keesom), polar-non polar interaction (Debye)and nonpolar-nonpolar interaction (London). However, other attractiveenergies may also be present, for example covalent bonding andelectrostatic bonding. So, in a more generalized form, the aboveequation is written as:

W˜2[√{square root over (γ₁ ^(d)γ₂ ^(d))}+√{square root over (γ₁ ^(p)γ₂^(p))}]+w _(c) +w _(e)  (10)

where w_(c) and w_(e) are the covalent and electrostatic adhesionenergies. Equation (10) describes that the adhesion energy is a functionof four surface energy parameters plus the covalent and electrostaticenergy, if any. An appropriate adhesion energy can be achieved by choiceof crack mitigating layer 130 material(s) to control van der Waals(and/or hydrogen) bonding and/or covalent bonding.

The adhesive energy of thin films is challenging to directly measure,including the adhesive energy between the crack mitigating layer 130 andthe glass substrate 120 or film 110. In contrast, the bond strength ofthe bond between two pieces of glass can be determined by inserting athin blade and measuring the crack length. In the case of a thin glassbonded to a thicker carrier with a coating or surface modification, thebond adhesion energy γ is related to the carrier Young's modulus E₁,carrier thickness t_(w1), thin glass modulus E₂, thin glass thicknesst_(w2), blade thickness t_(b), and crack length L by the followingequation, given by Equation (11) below.

$\begin{matrix}{\gamma = \frac{3t_{b}^{2}E_{1}t_{w\; 1}^{3}E_{2}t_{w\; 2}^{3}}{16{L^{4}\left( {{E_{1}t_{w\; 1}^{3}} + {E_{2}t_{w\; 2}^{3}}} \right)}}} & (11)\end{matrix}$

Equation (11) can be employed to approximate the adhesive energy betweenthe crack mitigating layer 130 and the glass substrate 120 or film 110(e.g., the adhesive energy at the interfaces 150 and 160, respectively).For example, the adhesive energy between two glass substrates (e.g., onethick and one thin) can be measured using Equation (11) as a control.Various glass substrate samples can then be prepared by conducting asurface treatment to a control glass substrate (e.g., a thick carriersubstrate). The surface treatment is exemplary of a particular crackmitigating film 130. After the surface treatment, the treated glasssubstrate is then bonded to a thin glass substrate comparable to thethin substrates employed as the control. The adhesive energy for thetreated samples can then be measured using Equation (11) and thencompared to the results obtained from comparable measurements to theglass control samples.

In one or more embodiments, the crack mitigating layer 130 may form apreferred path of crack propagation other than bridging between the film110 and the glass substrate 120. In other words, the crack mitigatinglayer 130 may deflect a crack forming in one of the film 110 and theglass substrate 120 and propagating toward the other of the film 110 andthe glass substrate 120 into the crack mitigating layer 130. In suchembodiments, the crack may propagate through the crack mitigating layer130 in a direction substantially parallel to at least one of the firstinterface 150 or the second interface 160. As depicted in FIG. 9A, thecrack becomes a cohesive failure 180, confined within the crackmitigating layer 130. As used herein, the term “cohesive failure”relates to crack propagation substantially confined within the crackmitigating layer 130.

The crack mitigating layer 130, when configured to develop a cohesivefailure 180 as shown in FIG. 9, provides a preferred path for crackpropagation in such embodiments. The crack mitigating layer 130 maycause a crack originating in the film 110 or the glass substrate 120 andentering into the crack mitigating layer 130 to remain in the crackmitigating layer. Alternatively or additionally, the crack mitigatinglayer 130 effectively confines a crack originating in one of the film110 and glass substrate 120 from propagating into the other of such filmand glass substrate. These behaviors may be characterized individuallyor collectively as crack deflection. In this way, the crack is deflectedfrom bridging between the film 110 and the glass substrate 120. In oneor more embodiments, the crack mitigating layer 130 may provide a lowtoughness layer or interface that exhibits a low fracture toughnessand/or a low critical strain energy release rate, which may promotecrack deflection into the crack mitigating layer 130 instead of throughthe crack mitigating layer into the film 110 and/or glass substrate 120.As used herein, “facilitate” includes creating favorable conditions inwhich the crack deflects into the crack mitigating layer 130 instead ofpropagating into the glass substrate 120 or the film 110. “Facilitate”may also include creating a less tortuous path for crack propagationinto and/or through the crack mitigating layer 130 instead of into theglass substrate 120 or the film 110.

The crack mitigating layer 130 may exhibit a relatively low fracturetoughness to provide a low toughness crack mitigating layer, as will bedescribed in greater detail below. In such embodiments, the crackmitigating layer 130 may exhibit a fracture toughness that is about 50%or less than 50% of the fracture toughness of either the glass substrate120 or the film 110. In more specific embodiments, the fracturetoughness of the crack mitigating layer 130 may be about 25% or lessthan 25% of the fracture toughness of either the glass substrate 120 orthe film 110. For example, the crack mitigating layer 130 may exhibit afracture toughness of about 1 MPa·m^(1/2) or less, 0.75 MPa·m^(1/2) orless, 0.5 MPa·m^(1/2) or less, 0.4 MPa·m^(1/2) or less, 0.3 MPa·m^(1/2)or less, 0.25 MPa·m^(1/2) or less, 0.2 MPa·m^(1/2) or less, 0.1MPa·m^(1/2) or less, and all ranges and sub-ranges there between.

In accordance with one or more embodiments, the crack mitigating layer130 may have an average strain-to-failure that is greater than theaverage strain-to-failure of the film 110. In one or more embodiments,the crack mitigating layer 130 may have an average strain-to-failurethat is equal to or greater than about 0.5%, 0.7%, 1%, 1.5%, 2%, or even4%. The crack mitigating layer 130 may have an average strain-to-failureof 0.6%, 0.8%, 0.9%, 1.1%, 1.2%, 1.3%, 1.4%, 1.6%, 1.7%, 1.8%, 1.9%,2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 5% or 6% or greater.In one or more embodiments, the film 110 may have an averagestrain-to-failure (crack onset strain) that is 1.5%, 1.0%, 0.7%, 0.5%,or even 0.4% or less. The film 110 may have an average strain-to-failureof 1.4%, 1.3%, 1.2%, 1.1%, 0.9%, 0.8%, 0.6%, 0.3%, 0.2%, 0.1% or less.The average strain-to-failure of the glass substrate 120 may be greaterthan the average strain-to-failure of the film 110, and in someinstances, may be greater than the average strain-to-failure of thecrack mitigating layer 130. In some specific embodiments, the crackmitigating layer 130 may have a higher average strain-to-failure thanthe glass substrate, to minimize any negative mechanical effect of thecrack mitigating layer on the glass substrate.

The crack mitigating layer 130 according to one or more embodiments mayhave a critical strain energy release rate (G_(IC)=K_(IC) ²/E) that isgreater than the critical strain energy release rate of the film 110. Inother examples, the crack mitigating layer may exhibit a critical strainenergy release rate that is less than 0.25 times or less than 0.5 timesthe critical strain energy release rate of the glass substrate. Inspecific embodiments, the critical strain energy release rate of thecrack mitigating layer can be about 0.1 kJ/m² or less, about 0.09 kJ/m²or less, about 0.08 kJ/m² or less, about 0.07 kJ/m² or less, about 0.06kJ/m² or less, about 0.05 kJ/m² or less, about 0.04 kJ/m² or less, about0.03 kJ/m² or less, about 0.02 kJ/m² or less, about 0.01 kJ/m² or less,about 0.005 kJ/m² or less, about 0.003 kJ/m² or less, about 0.002 kJ/m²or less, about 0.001 kJ/m² or less; but in some embodiments, greaterthan about 0.0001 kJ/m² (i.e. greater than about 0.1 J/m²).

The crack mitigating layer 130 may have a refractive index that isgreater than the refractive index of the glass substrate 120. In one ormore embodiments, the refractive index of the crack mitigating layer 130may be less than the refractive index of the film 110. In a morespecific embodiment, the refractive index of the crack mitigating layer130 may be between the refractive index of the glass substrate 120 andthe film 110. For example, the refractive index of the crack mitigatinglayer 130 may be in the range from about 1.45 to about 1.95, from about1.5 to about 1.8, or from about 1.6 to about 1.75. Alternatively, thecrack mitigating layer may have a refractive index that is substantiallythe same as the glass substrate, or a refractive index that is not morethan 0.05 index units greater than or less than the glass substrate overa substantial portion of the visible wavelength range (e.g. from 450 to650 nm).

In one or more embodiments, the crack mitigating layer 130 is able towithstand high temperature processes. Such processes can include vacuumdeposition processes such as chemical vapor deposition (e.g., plasmaenhanced chemical vapor deposition), physical vapor deposition (e.g.,reactive or nonreactive sputtering or laser ablation), thermal or e-beamevaporation and/or atomic layer deposition. In one or more specificembodiments, the crack mitigating layer is able to withstand a vacuumdeposition process in which the film 110 and/or other films disposed onthe glass substrate 120 are deposited on the crack mitigating layer 130via vacuum deposition. As used herein, the term “withstand” includes theresistance of the crack mitigating layer 130 to temperatures exceeding100° C., 200° C., 300° C., 400° C., 500° C., 600° C. and potentiallyeven greater temperatures. In some embodiments, the crack mitigatinglayer 130 may be considered to withstand the vacuum deposition ortemperature treatment process if the crack mitigating layer 130experiences a weight loss of 10% or less, 8% or less, 6% or less, 4% orless, 2% or less or 1% or less, after deposition of the film 110 and/orother films on the glass substrate (and on the crack mitigating layer130). The deposition process (or testing after the deposition process)under which the crack mitigating layer experiences weight loss caninclude temperatures of about 100° C. or greater, 200° C. or greater,300° C. or greater, 400° C. or greater; environments that are rich in aspecific gas (e.g., oxygen, nitrogen, argon etc.); and/or environmentsin which deposition may be performed under high vacuum (e.g. 10⁻⁶ Torr),under atmospheric conditions and/or at pressures therebetween (e.g., 10mTorr). As will be discussed herein, the material utilized to form thecrack mitigating layer 130 may be specifically selected for its hightemperature tolerances (i.e., the ability to withstand high temperatureprocesses such as vacuum deposition processes) and/or its environmentaltolerances (i.e., the ability to withstand environments rich in aspecific gas or at a specific pressure). These tolerances may includehigh temperature tolerance, high vacuum tolerance, low vacuumoutgassing, a high tolerance to plasma or ionized gases, a hightolerance to ozone, a high tolerance to UV, a high tolerance tosolvents, or a high tolerance to acids or bases. In some instances, thecrack mitigating layer 130 may be selected to pass an outgassing testaccording to ASTM E595. In one or more embodiments, the articleincluding the crack mitigating layer 130 may exhibit an improved averageflexural strength over articles without the crack mitigating layer 130.In other words, articles that include a glass substrate 120, a film 110and a crack mitigating layer 130 exhibit greater average flexuralstrength than articles that include the glass substrate 120 and the film110 but no crack mitigating layer 130.

In one or more embodiments, the crack mitigating layer 130 may include aplasma-polymerized polymer. Plasma polymerization includes thedeposition of a thin polymer film under atmospheric or reduced pressureand plasma excitation (e.g., DC or RF parallel plate, InductivelyCoupled Plasma (ICP) Electron Cyclotron Resonance (ECR) downstreammicrowave or RF plasma), from source gases. Exemplary source gasesinclude fluorocarbon sources (including CF₄, CHF₃, C₂F₆, C₃F₆, C₂F₂,CH₃F, C₄F₈, chlorofluoro carbons, or hydrochlorofluoro carbons),hydrocarbons for example alkanes (including methane, ethane, propane,butane), alkenes (including ethylene, propylene), alkynes (includingacetylene), and aromatics (including benzene, toluene), hydrogen, andother gas sources for example SF₆. Plasma polymerization creates a layerof highly cross-linked material. Control of reaction conditions andsource gases can be used to control the film thickness, density, andchemistry to tailor the functional groups to the desired application.

In one or more embodiments, the plasma-polymerized polymer may includeone or more of plasma-polymerized fluoropolymer, plasma-polymerizedhydrocarbon polymer, plasma-polymerized siloxane polymer andplasma-polymerized silane polymer. Where the plasma-polymerized polymerincludes a plasma-polymerized fluorocarbon, such material may be avacuum-deposited material formed from a polymer forming fluorocarbonsource gas(es), as described above, and a fluorinated etchant.Accordingly, the crack mitigating layer may include fluorine in someembodiments. The fluorine can be derived from a fluorine-containing gas(e.g., CHF₃, C₄F₈, CF₄, C₂F₆, C₃F₈, NF₃, and SF₆). In such embodiments,the fluorocarbon source gas and fluorinated etchant are flowedsequentially or simultaneously to achieve the desired layer andthickness of layer.

In one or more embodiments, the plasma-polymerized hydrocarbon mayinclude a vacuum-deposited material formed from a volatile gas andoptionally hydrogen. The volatile gas can include an alkane(C_(n)H_(2n+2)), an alkene (C_(n)H_(2n)), an alkyne (C_(n)H_(2n−2)), orcombinations thereof, where n<8. In embodiments utilizing aplasma-polymerized silane polymer, such material may be vacuum-depositedmaterial and may be formed from a silane source material and optionallyan oxidizer. The silane source material may include the formulationR_(x)SiX_(4−x) where R is an alkyl or aryl organic group and X comprisesone of a hydrogen, a halide, or an alkoxy group. The optional oxidizermay include oxygen, ozone, nitrous oxide, carbon dioxide, water vapor,hydrogen peroxide and/or combinations thereof.

In one or more embodiments, the crack mitigating layer 130 may include asilane, which is distinguished from the plasma-polymerized silanepolymer. In one or more embodiments, the silane may include asolution-deposited silane and/or vapor-deposited silane, which is formedwithout the use of plasma. The silane may include an aliphatic silaneand/or an aromatic silane. In some embodiments, the silane may includethe formulation R_(x)SiX_(4−x) where R comprises a fluorine, alkyl oroptionally-fluorinated or chlorinated aryl organic group and X comprisesa halide or an alkoxy group.

In one or more embodiments, the crack mitigating layer may include ametal, such as Al, Cu, Ti, Fe, Ag, Au, or other similar metals andcombinations thereof. In some embodiments, very thin metal films (e.g.,in the range from about 1 to about 100 nm, from about 1 nm to about 50nm, and/or from about 1 nm to about 10 nm) can be used to modify theadhesion at one or more interfaces while maintaining relatively highoptical transmittance (e.g. greater than 50% or greater than 80% opticaltransmittance).

In one or more embodiments, the crack mitigating layer 130 may include:porous oxides, such as SiO₂, SiO, SiO_(x), Al₂O₃; TiO₂, ZrO₂, Nb₂O₅,Ta₂O₅, GeO₂ and similar material(s) known in the art; porous versions ofthe films mentioned elsewhere herein, for example porousindium-tin-oxide, porous aluminum-zinc-oxide, or porousfluorinated-tin-oxide; porous nitrides or carbides, for example Si₃N₄,AlN, TiN, TiC; porous oxycarbides and oxy-carbo-nitrides, for example,SiC_(x)O_(y) and SiC_(x)O_(y)N_(z); porous semiconductors such as Si orGe; porous oxynitrides such as SiO_(x)N_(y), AlO_(x)N_(y), orSiAl_(x)O_(y)N_(z); porous metals such as Al, Cu, Ti, Fe, Ag, Au, andother metals.

In some cases, the crack mitigating layer 130 includes an inorganicmaterial. The inorganic material can include a metal fluoride (e.g.,CaF₂, BaF₂, AlF₃, MgF₂, SrF₂, LaF₃ and lanthanide series trifluorides).In some embodiments, the crack mitigating layer 130 includes two or moremetal fluorides. Metal fluorides employed in the crack mitigating layer130 can be deposited as discrete films on the glass substrate 120 by avariety of methods including but not limited to various vacuumdeposition techniques, e.g., e-beam evaporation. Advantageously, thediscrete metal fluoride films, and other inorganic materials, employedin crack mitigating layer 130 can be deposited as discrete films in situwith the subsequent deposition of film 110 using such vacuum depositiontechniques. Cleanliness can be maintained during such multiple-filmdeposition sequences. Further, manufacturing time can be reduced by thedeposition of multiple films on the glass substrate 120 in a singlevacuum chamber.

The inorganic material contained in the crack mitigating layer 130 canalso include a reaction product derived at least in part from the glasssubstrate 120. In some of these embodiments, the crack mitigating layer130 can be developed through the deposition of a plasma-polymerizedpolymer on the glass substrate 120 and/or the selective etching ofcertain glass constituents in the surface of the glass substrate 120(e.g., at the interface 150). In some cases, the deposition and/oretching is performed using a low pressure plasma treatment (e.g., about50 mTorr). According to some embodiments, fluorine-containing sourcegases are employed to develop the plasma-polymerized polymer and/or etchthe glass substrate 120 including but not limited to CHF₃, C₄F₈, CF₄,C₂F₆, C₃F₈, NF₃, and SF₆.

As depicted in FIGS. 10A and 10B, in some exemplary embodiments, therelative ratio between CHF₃ and CF₄ can be controlled to effectplasma-assisted deposition of the crack mitigating layer 130 and/oretching of the glass substrate 120 to form or develop the crackmitigating layer 130. A high percentage of CF₄ (i.e., CF₄/(CF₄+CHF₃) onthe x-axis of FIGS. 10A and 10B approaches 1.0 and/or exceeds 1.0) forexample, can be employed to effectively etch Si and B from the surfaceof the glass, while at the same time fluorinating Al, Ca, and Mg, alsopresent at the surface of the glass. The development of these fluorides,and others, can reduce the adhesive energy between the crack mitigatinglayer 130 and the glass substrate 120 and the film 110. A highpercentage of CHF₃ (i.e., CF₄/(CF₄+CHF₃) on the x-axis of FIGS. 10A and10B approaches 0), for example, can be employed to develop a carbon-richfluoropolymer layer or region at the surface of the glass substrate 120,serving as a crack mitigating layer 130. Indeed, FIG. 10A demonstratesrelatively high levels of carbon when pure CHF₃ is employed in aplasma-assisted development of crack mitigating layer 130. Moreover, thedevelopment of such carbon-rich fluoropolymer films, and other polymericfilms, to serve as the crack mitigating layer 130 can also reduce theadhesive energy between layer 130 and the glass substrate 120 and thefilm 110.

In other embodiments, fluorine-containing etchant gases (e.g., CF₄,C₂F₆, C₃F₈, NF₃, and SF₆) can be used with plasma-assisted treatments toetch Si and/or B from the SiO₂ and B₂O₃ present at the surface of theglass substrate 120. At the same time, these etchants can fluorinate theAl, Ca and/or Mg in the Al₂O₃, CaO and MgO constituents in the glasssubstrate 120. The development of these metal fluorides from metaloriginally contained in the substrate, e.g., AlF_(x), CaF_(x) and/orMgF_(x), and/or local reductions in the amount of SiO₂ and B₂O₃ in thecrack mitigating layer 130 can reduce the overall adhesive energybetween the glass substrate 120 and film 110, even after subsequent hightemperature treatments. In addition, fluorine-containing polymer forminggases (e.g., CHF₃, C₄F₈) can be used to develop fluoropolymer filmsand/or regions at the surface of the glass substrate 120 to form a crackmitigating layer 130. Combinations of these metal fluorides andfluoropolymer films, created via different compositions of suchfluorine-containing gases, can also be employed to generate films and/orregions at the surface of the glass substrate 120 that can serve as acrack mitigating layer 130. Crack mitigating layers 130 formed in thisfashion also can reduce the overall adhesive energy between the glasssubstrate 120 and film 110 with limited sensitivity to subsequentthermal processing of the articles containing such substrates and filmsand/or elevated temperatures associated with the creation of the film110.

In one or more embodiments, the crack mitigating layer 130 may be acontinuous layer or a discontinuous layer. Where the crack mitigatinglayer is a discontinuous layer, the first opposing surface 122 on whichthe crack mitigating layer 130 is disposed may include exposed areas 132(or areas that do not include the crack mitigating layer 130) and areasthat include the crack mitigating layer 130, as shown in FIGS. 5A-5C.The pattern of the crack mitigating layer 130 may include discreteislands of the material surrounded by exposed areas 132 (or areas thatdo not include the crack mitigating layer 130) as shown in FIG. 5B.Alternatively, the crack mitigating layer 130 may form a continuousmatrix of material with exposed areas 132 (or areas that do not includethe crack mitigating layer 130) surrounded by the crack mitigating layer130 as shown in FIG. 5C. The crack mitigating layer 130 may cover about50%, about 60%, about 70%, about 80%, about 90% or about 100% of thearea of the first opposing surface 122. The thickness of the crackmitigating layer 130 may be uniform along substantially all of the areasof the first opposing surface on which it is disposed. In one or morealternative embodiments, the thickness of the crack mitigating layer mayvary to provide areas of less thickness and areas of greater thickness.The variation in thickness may be present where the crack mitigatinglayer is continuous or discontinuous.

The crack mitigating layer 130 may be disposed between the film 110 andthe glass substrate 120 by a variety of methods. The crack mitigatinglayer 130 can be disposed using vacuum deposition techniques, forexample, chemical vapor deposition (e.g., plasma enhanced chemical vapordeposition, atmospheric pressure chemical vapor deposition, orplasma-enhanced atmospheric chemical vapor deposition), physical vapordeposition (e.g., reactive or nonreactive sputtering, thermalevaporation, e-beam evaporation, or laser ablation), thermal, resistive,or e-beam evaporation and/or atomic layer deposition. The crackmitigating layer 130 of one or more embodiments may exhibit highertemperature tolerance, robustness to UV ozone or plasma treatments, UVtransparency, robustness to environmental aging, low outgassing invacuum, and the like. In instances where the film is also formed byvacuum deposition, both the crack mitigating layer and the film can beformed in the same or similar vacuum deposition chamber or using thesame or similar coating equipment.

The crack mitigating layer 130 may also be disposed using liquid-baseddeposition techniques, for example sol-gel coating or polymer coatingmethods, for example spin, spray, slot draw, slide, wire-wound rod,blade/knife, air knife, curtain, roller, gravure coating among othersand other methods known in the art.

In one or more embodiments, the crack mitigating layer 130 may include aporous layer, or more specifically, a nanoporous layer. As used herein,the term “nanoporous” includes materials with traditionally-defined“pores” (e.g., openings or voids) and also includes materials that arecharacterized by a lower density or a lower elastic modulus than isexpected for fully dense materials having the same or similar chemicalcomposition. Thus, the “pores” in the nanoporous layer may take the formof columnar voids, atomic vacancies, spherical pores, intersticesbetween grains or particles, regions of low or varying density, or anyother geometry that leads to a macroscopic decrease in density orelastic modulus for the nanoporous layer. The volume fraction ofporosity can be estimated from refractive index measurements using knownmethods, for materials with nanoscale pores and no light scattering orvery low light scattering. In one or more embodiments, the volumefraction of porosity may be greater than about 5%, greater than about10%, or greater than about 20%. In some embodiments the volume fractionof porosity may be less than about 90%, or less than about 60%, topreserve mechanical durability of the nanoporous layers during handlingand end use.

The nanoporous layer may be substantially optically transparent and freeof light scattering, for example having an optical transmission haze of10% of less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less,4% or less, 3% or less, 2% or less, 1% or less and all ranges andsub-ranges therebetween. The transmission haze of the nanoporous layermay be controlled by controlling the average sizes of pores, as definedherein. Exemplary average pore sizes in the nanoporous layer may include200 nm or less, 100 nm or less, 90 nm or less, 80 nm or less, 70 nm orless, 60 nm or less, 50 nm or less, 40 nm or less, 30 nm or less, 20 nmor less, 10 nm or less, 5 nm or less and all ranges and sub-rangestherebetween. These pore sizes can be estimated from light scatteringmeasurements, or directly analyzed using transmission electronmicroscopy (TEM) and other known methods.

In one or more embodiments, the nanoporous layer in the crack mitigatinglayer 130 may include an inorganic material. The inorganic material inthe nanoporous layer can include a metal and/or fluorine in some cases.According to some embodiments, the inorganic material in the nanoporouslayer can include a metal fluoride (e.g., CaF₂, BaF₂, AlF₃, MgF₂, SrF₂,LaF₃, YF₃ and lanthanide series trifluorides). The inorganic materialcontained in the crack mitigating layer (e.g., crack mitigating layer130) in the form of a nanoporous layer can also include a reactionproduct derived at least in part from the substrate (e.g., glasssubstrate 120). In one or more specific embodiments, the crackmitigating layer only includes a nanoporous layer and is nanoporousthroughout. The nanoporous layer may include inorganic materials andmay, alternatively, exclude organic materials. In one or moreembodiments, the crack mitigating layer may include an inorganicnanoporous layer that exhibits low intrinsic film stresses. In specificembodiments, such crack mitigating layers may be formed using techniquesthat control intrinsic film stresses (e.g., vacuum deposition) in thecrack mitigating layer (relative to, for example, some sol-gel coatingprocesses). The control of intrinsic film stresses may also enablecontrol over other mechanical properties such as strain-to-failure ofthe crack mitigating layer.

Porosity and mechanical properties of the crack mitigating layer can becontrolled using careful control of deposition methods such as a slightoverpressure of gas in the vacuum chamber, low temperature deposition,deposition rate control, and plasma and/or ion-beam energy modification.Although vapor deposition methods are commonly used, other known methodscan be used to provide a crack mitigating layer with the desiredporosity and/or mechanical properties. For example, the crack mitigatinglayer including a nanoporous layer can also be formed by wet-chemistryor sol-gel methods, such as spin coating, dip coating, slot/slitcoating, roller coating, gravure coating, and spray coating. Porositycan be introduced to wet-coated nanoporous layers by use of a poreformer (such as a block copolymer pore former) which is later dissolvedor thermally decomposed, phase separation methods, or the casting of aparticulate or nanoparticulate layer where interstices between particlesremain partially void.

In some embodiments the nanoporous layer may exhibit a similarrefractive index to either the glass substrate and/or film and/oradditional layers (as described herein), to minimize opticalinterference effects. Additionally or alternatively, the nanoporouslayer may exhibit a refractive index that is tuned to achieveanti-reflective interference effects. The refractive index of thenanoporous layer can be engineered somewhat by controlling thenanoporosity of the nanoporous layer. For example, in some cases it maybe desirable to choose a material with a relatively high refractiveindex, such as Al₂O₃, TiO₂, Nb₂O₅, Si₃N₄, or AlN, which when made into ananoporous layer with a targeted porosity level can exhibit anintermediate refractive index in the range from about 1.4 to about 1.8or a refractive index that approximates the glass substrate (e.g., inthe range from about 1.45 to about 1.6). The refractive index of thenanoporous layer can be related to the porosity level using “effectiveindex” models that are known in the art.

The thickness (which includes an average thickness where the thicknessof the crack mitigating layer varies) of the crack mitigating layer 130may be in the range of about 0.001 μm to about 10 μm (1 nm to 10,000 nm)or in the range from about 0.005 μm to about 0.5 μm (5 nm to about 500nm), from about 0.01 μm to about 0.5 μm (10 nm to about 500 nm), fromabout 0.02 μm to about 0.2 μm (20 nm to about 200 nm); however in somecases the film can be much thinner, for example, the crack mitigatinglayer 130 may be a single-molecule “monolayer” having a thickness ofabout 0.1 nm to about 1 nm. In one or more embodiments, the thickness ofthe crack mitigating layer 130 is in the range from about 0.02 μm toabout 10 μm, from about 0.03 μm to about 10 μm, from about 0.04 μm toabout 10 μm, from about 0.05 μm to about 10 μm, from about 0.06 μm toabout 10 μm, from about 0.07 μm to about 10 μm, from about 0.08 μm toabout 10 μm, from about 0.09 μm to about 10 μm, from about 0.1 μm toabout 10 μm, from about 0.01 μm to about 9 μm, from about 0.01 μm toabout 8 μm, from about 0.01 μm to about 7 μm, from about 0.01 μm toabout 6 μm, from about 0.01 μm to about 5 μm, from about 0.01 μm toabout 4 μm, from about 0.01 μm to about 3 μm, from about 0.01 μm toabout 2 μm, from about 0.01 μm to about 1 micron, from about 0.02 μm toabout 1 micron, from about 0.03 to about 1 μm, from about 0.04 μm toabout 0.5 μm, from about 0.05 μm to about 0.25 μm or from about 0.05 μmto about 0.15 μm. In one or more specific embodiments, the thickness ofthe crack mitigating layer may be about 30 nm or less, about 20 nm orless, about 10 nm or less, about 5 nm or less, about 4 nm or less, about3 nm or less, about 2 nm or less or about 1 nm or less.

In one or more embodiments, thicknesses of the glass substrate 120, film110 and/or crack mitigating layer 130 may be specified in relation toone another. For example, the crack mitigating layer may have athickness that is less than or equal to about 10 times the thickness ofthe film. In another example, where a film 110 has a thickness of about85 nm, the crack mitigating layer 130 may have a thickness of about 850nm or less. In yet another example, the thickness of the crackmitigating layer 130 may be in the range from about 35 nm to about 80 nmand the film 110 may have a thickness in the range from about 30 nm toabout 300 nm. In one variant, the crack mitigating layer may have athickness that is less than or equal to about 9 times, 8 times, 7 times,6 times, 5 times, 4 times, 3 times or two times the thickness of thefilm. In another variant, the thickness of the film and the thickness ofthe crack mitigating film are each less than about 10 μm, less thanabout 5 μm, less than about 2 μm, less than about 1 μm, less than about0.5 μm, or less than about 0.2 μm. The ratio of the crack mitigatinglayer 130 thickness to the film 110 thickness may be, in someembodiments, in the range from about 1:1 to about 1:8, in the range fromabout 1:2 to about 1:6, in the range from about 1:3 to about 1:5, or inthe range from about 1:3 to about 1:4. In another variant, the thicknessof the crack mitigating layer is less than about 0.1 μm and thethickness of the film is greater than the crack mitigating layer.

One or more embodiments of the article include a crack mitigating layer130 comprising a plasma-polymerized polymer, a silane, a metal orcombinations thereof. In such embodiments, when the crack mitigatinglayer 130 is utilized, the film 110 maintains functional properties(e.g., optical properties, electrical properties and mechanicalproperties) and the article 100 retains its average flexural strength.In such embodiments, the film 110 may include one or more transparentconductive oxide layers, such as indium-tin-oxide layers or scratchresistant layer, such as AlOxNy, AlN and combinations thereof. Inaddition, the glass substrate 120 may be strengthened, or morespecifically, chemically strengthened.

Additionally or alternatively, the film 110 including one or more of anindium-tin-oxide layer, a scratch-resistant layer (e.g., AlOxNy, AlN andcombinations thereof), an easy-to-clean layer, an anti-reflective layer,an anti-fingerprint layer and the like, and the crack mitigating layer130 comprising a plasma-polymerized polymer, a silane, a metal orcombinations thereof, form a stack, wherein the stack has an overall lowoptical reflectance. For example, the overall (or total) reflectance ofsuch a stack may be 15% or less, 10% or less, 8% or less, 7% or less,6.5% or less, 6% or less, 5.5% or less across a visible wavelength rangefrom 450-650 nm, 420-680 nm, or even 400-700 nm. The reflectance numbersabove may be present in some embodiments including the reflectance fromone bare (or uncoated) glass interface, which is approximately 4%reflectance from the uncoated glass interface alone, or may becharacterized as the reflectance for a first major surface of a glasssubstrate and the films and layers (and associated interfaces) disposedon the first major surface (excluding the 4% reflectance from anuncoated second major surface of the glass substrate). The reflectancefrom the film stack structure and film-glass coated interfaces alone(subtracting out the reflectance of the uncoated glass interface) may beless than about 5%, 4%, 3%, 2%, or even less than about 1.5% across avisible wavelength range from 450-650 nm, 420-680 nm, or even 400-700nm, in some cases when one or more major surfaces of the glass substrateis covered by a typical encapsulant (i.e. an additional film or layer)having an encapsulant refractive index of about 1.45-1.65. In addition,the stack structure may exhibit a high optical transmittance, whichindicates both low reflectance and low absorptance, according to thegeneral relationship: Transmittance=100%−Reflectance−Absorptance. Thetransmittance values for the stack structure (when neglectingreflectance and absorptance associated with the glass substrate orencapsulant layers alone) may be greater than about 75%, 80%, 85%, 90%,95%, or even 98% across a visible wavelength range from 450-650 nm,420-680 nm, or even 400-700 nm.

One or more embodiments of the article include a crack mitigating layer130 comprising nanoporous, vapor-deposited SiO₂. In such embodiments,when the crack mitigating layer 130 is utilized, the film 110 maintainsfunctional properties (e.g., optical properties, electrical propertiesand mechanical properties) and the article 100 retains its averageflexural strength, or has an improved average flexural strength relativeto a similar article comprising film 110 and glass substrate 120 withoutthe crack mitigating layer 130. In such embodiments, the film 110 mayinclude one or more transparent conductive oxide layers, such asindium-tin-oxide layers, a scratch resistant layer, an easy-to-cleanlayer, an anti-reflective layer, an anti-fingerprint layer and the like.In addition, the glass substrate 120 may be strengthened, or morespecifically, chemically strengthened. In these embodiments, use of thecrack-mitigating layers described herein may be utilized for someapplications because of the temperature, vacuum, and environmentaltolerance factors mentioned elsewhere herein.

The optical properties of the article 100 may be adjusted by varying oneor more of the properties of the film 110, crack mitigating layer 130and/or the glass substrate 120. For example, the article 100 may exhibita total reflectance of 15% or less, 10% or less, 8% or less, 7% or less,6.9% or less, 6.8% or less, 6.7% or less, 6.6% or less, 6.5% or less,6.4% or less, 6.3% or less, 6.2% or less, 6.1% or less and/or 6% orless, over the visible wavelength range from about 400 nm to about 700nm. Ranges may further vary as specified hereinabove, and ranges for thefilm stack/coated glass interfaces alone are listed hereinabove. In morespecific embodiments, the article 100 described herein, may exhibit alower average reflectance and greater average flexural strength thanarticles without a crack mitigating layer 130. In one or morealternative embodiments, at least two of optical properties, electricalproperties or mechanical properties of the article 100 may be adjustedby varying the thickness(es) of the glass substrate 120, film 110 and/orthe crack mitigating layer 130. Additionally or alternatively, theaverage flexural strength of the article 100 may be adjusted or improvedby modifying the thickness(es) of the glass substrate 120, film 110and/or the crack mitigating layer 130.

The article 100 may include one or more additional films disposed on theglass substrate. In one or more embodiments, the one or more additionalfilms may be disposed on the film 110 or on the opposite major surfacefrom the film. The additional film(s) may be disposed in direct contactwith the film 110. In one or more embodiments, the additional film(s)may be positioned between: 1) the glass substrate 120 and the crackmitigating layer 130; or 2) the crack mitigating layer 130 and the film110. In one or more embodiments, both the crack mitigating layer 130 andthe film 110 may be positioned between the glass substrate 120 and theadditional film(s). The additional film(s) may include a protectivelayer, an adhesive layer, a planarizing layer, an anti-splinteringlayer, an optical bonding layer, a display layer, a polarizing layer, alight-absorbing layer, reflection-modifying interference layers,scratch-resistant layers, barrier layers, passivation layers, hermeticlayers, diffusion-blocking layers and combinations thereof, and otherlayers known in the art to perform these or related functions. Examplesof suitable protective or barrier layers include layers containingSiO_(x), SiN_(y), SiO_(x)N_(y), other similar materials and combinationsthereof. Such layers can also be modified to match or complement theoptical properties of the film 110, the crack mitigating layer 130and/or the glass substrate 120. For example, the protective layer may beselected to have a similar refractive index as the crack mitigatinglayer 130, the film 110, or the glass substrate 120. It will be apparentto those of ordinary skill in the art that multiple additional film(s)with varying refractive indices and/or thicknesses can be inserted forvarious reasons. The refractive indices, thicknesses and otherproperties of the additional films (as well as the crack mitigatinglayer 130 and the film 110) may be further modified and optimized,without departing from the spirit of the disclosure. In other cases, forexample, alternate film designs can be employed where the crackmitigating layer 130 may have a higher refractive index than the film.

In one or more embodiments, the articles 100 described may be used ininformation display devices and/or touch-sensing devices. In one or morealternative embodiments, the article 100 may be part of a laminatestructure, for example as a glass-polymer-glass laminated safety glassto be used in automotive or aircraft windows. An exemplary polymermaterial used as an interlayer in these laminates is PVB (Polyvinylbutyral), and there are many other interlayer materials known in the artthat can be used. In addition, there are various options for thestructure of the laminated glass, which are not particularly limited.The article 100 may be curved or shaped in the final application, forexample as in an automotive windshield, sunroof, or side window. Thethickness of the article 100 can vary, for either design or mechanicalreasons; for example, the article 100 can be thicker at the edges thanat the center of the article. The article 100 may be acid polished orotherwise treated to remove or reduce the effect of surface flaws.

A second aspect of the present disclosure pertains to cover glassapplications that utilize the articles described herein. In one or moreembodiments, the cover glass may include a laminated article with aglass substrate 120 (which may be strengthened or not strengthened), ascratch-resistant film including hard material(s) such as AlO_(x)N_(y),AlN, SiO_(x)N_(y), SiAl_(v)O_(x)N_(y), Si₃N₄ and combinations thereof,and the crack mitigating layer 130. The laminated article may includeone or more additional film(s) for reducing the reflection and/orproviding an easy to clean or anti-fingerprint surface on the laminatedarticle.

Another aspect of the present disclosure pertains to touch-sensingdevices including the articles described herein. In one or moreembodiments, the touch sensor device may include a glass substrate 120(which may be strengthened or not strengthened), a film 110 comprising atransparent conductive oxide and a crack mitigating layer 130. Thetransparent conductive oxide may include indium-tin-oxide,aluminum-zinc-oxide, fluorinated tin oxide, or others known in the art.In one or more embodiments, the film 110 is discontinuously disposed onthe glass substrate 120. In other words, the film 110 may be disposed ondiscrete regions of the glass substrate 120. The discrete regions withthe film form patterned or coated regions (not shown), while thediscrete regions without the film form unpatterned or uncoated regions(not shown). In one or more embodiments, the patterned or coated regionsand unpatterned or uncoated regions are formed by disposing the film 110continuously on a surface of the glass substrate 120 and thenselectively etching away the film 110 in the discrete regions so thatthere is no film 110 in those discrete regions. The film 110 may beetched away using an etchant such as HCl or FeCl₃ in aqueous solutions,such as the commercially available TE-100 etchant from Transene Co. Inone or more embodiments, the crack mitigating layer 130 is notsignificantly degraded or removed by the etchant. Alternatively, thefilm 110 may be selectively deposited onto discrete regions of a surfaceof the glass substrate 120 to form the patterned or coated regions andunpatterned or uncoated regions.

In one or more embodiments, the uncoated regions have a totalreflectance that is similar to the total reflectance of the coatedregions. In one or more specific embodiments, the unpatterned oruncoated regions have a total reflectance that differs from the totalreflectance of the patterned or coated regions by about 5% or less, 4.5%or less, 4% or less, 3.5% or less, 3% or less, 2.5% or less, 2.0% orless, 1.5% or less or even 1% or less across a visible wavelength in therange from about 450 nm to about 650 nm, from about 420 nm to about 680nm or even from about 400 nm to about 700 nm.

In accordance with another aspect of the present disclosure, articles100 including both a crack mitigating layer 130 and a film 110, whichmay include indium-tin-oxide or other transparent conductive oxides,exhibit resistivity that is acceptable for use of such articles in touchsensing devices. In one or more embodiments, the films 110, when presentin the articles disclosed herein, exhibit a sheet resistance of about100 ohm/square or less, 80 ohm/square or less, 50 ohm/square or less, oreven 30 ohm/square or less. In such embodiments, the film may have athickness of about 200 nm or less, 150 nm or less, 100 nm or less, 80 nmor less, 50 nm or less or even 35 nm or less. In one or more specificembodiments, such films, when present in the article, exhibit aresistivity of 10×10⁻⁴ ohm-cm or less, 8×10⁻⁴ ohm-cm or less, 5×10⁻⁴ohm-cm or less, or even 3×10⁻⁴ ohm-cm or less. Thus, the films 110, whenpresent in the articles 100 disclosed herein can favorably maintain theelectrical and optical performance expected of transparent conductiveoxide films and other such films used in touch sensor applications,including projected capacitive touch sensor devices.

The disclosure herein can also be applied to articles which havearticles that are not interactive or for display; for example, sucharticles may be used in a case in which a device has a glass front sidethat is used for display and can be interactive, and a back side thatmight be termed “decorative” in a very broad sense, meaning thatbackside can be “painted” some color, have art work or information aboutthe manufacturer, model and serial number, texturing or other features.

Another aspect of the present disclosure pertains to a method of formingan article 100. In one or more embodiments, such methods includeproviding a glass substrate 120, disposing a film 110 on a first majorsurface of the glass substrate to create an effective interfacetherebetween and controlling the effective adhesion energy of theeffective interface. In one or more embodiments, the method includescontrolling the effective adhesion energy to less than about 4 J/m². Inone or more embodiments, controlling the effective adhesion energyincludes disposing a crack mitigating layer 130 on a surface (e.g., oneor more of the major surfaces 122, 124 and/or one or more minorsurfaces) of the glass substrate 120 before disposing the film. In otherwords, controlling the effective adhesion energy includes disposing acrack mitigating layer 130 between the film 110 and the glass substrate120.

In the method of forming an article 100, the crack mitigating layer 130can include fluorine and, in some cases, may further include a metal.According to some embodiments, the crack mitigating layer 130 includes ametal fluoride. The crack mitigating layer 130 can also include aninorganic metal fluoride compound that contains the fluorine. In someembodiments, the fluorine can be derived from one or morefluorine-containing gases (e.g., CHF₃, C₄F₈, CF₄, C₂F₆, C₃F₈, NF₃, andSF₆). According to some other embodiments of the method of forming anarticle 100, the step for controlling the effective adhesion energy ofthe interface can include a step for effecting a reaction between thefluorine-containing gas and the substrate (e.g., glass substrate 120)such that the metal in the crack mitigating layer 130 is derived atleast in part from the substrate.

In one or more embodiments, the method includes disposing the film 110and/or the crack mitigating layer 130 via a vacuum deposition process.In particular embodiments, such vacuum deposition processes may utilizetemperatures of at least about 100° C., 200° C., 300° C., 400° C. andall ranges and sub-ranges therebetween. In some embodiments, the crackmitigating layer 130 may be formed by a wet process.

In one or more specific embodiments, the method includes controlling thethickness(es) of the crack mitigating layer 130 and/or the film 110.Controlling the thickness(es) of the crack mitigating layer and/or filmsdisclosed herein may be performed by controlling one or more processesfor forming the crack mitigating layer and/or films so that the crackmitigating layer and/or films are applied having a desired or definedthickness. In an even more specific embodiment, the method includescontrolling the thickness(es) of the crack mitigating layer 130 and/orthe film 110 to maintain the average flexural strength of the glasssubstrate 120 and/or the functional properties of the film 110.

In one or more alternative embodiments, the method includes controllingthe continuity of the crack mitigating layer 130 and/or the film.Controlling the continuity of the crack mitigating layer 130 may includeforming a continuous crack mitigating layer and removing a selectedportion(s) of the crack mitigating layer to create a discontinuous crackmitigating layer. In other embodiments, controlling the continuity ofthe crack mitigating layer may include selectively forming the crackmitigating layer to form a discontinuous crack mitigating layer. Suchembodiments may use a mask, an etchant and combinations thereof tocontrol the continuity of the crack mitigating layer.

In one or more alternative embodiments, the method includes controllingthe surface energy of the crack mitigating layer 130 when it is disposedon the glass substrate 120, but before deposition of the film 110.Controlling the surface energy of the crack mitigating layer at thisintermediate stage of fabrication may be useful for establishing arepeatable fabrication process. In one or more embodiments, the methodincludes controlling the surface energy of the crack mitigating layer130 (as measured when the crack mitigating layer 130 is uncovered andexposed to air) to less than about 70 mJ/m² or less, 60 mJ/m² or less,50 mJ/m² or less, 40 mJ/m² or less, 30 mJ/m² or less, 20 mJ/m² or less,but in some cases, greater than about 15 mJ/m². In one or moreembodiments, the foregoing surface energy values and ranges include bothpolar and dispersion components and may be measured by fitting a knowntheoretical model developed by S. Wu (1971) to three contact angles ofthree test liquids; water, diodomethane and hexadecane. (Reference: S.Wu, J. Polym. Sci C, 34, 19, 1971).

In one or more embodiments, the method may include creating porosity inthe crack mitigating layer 130. The method may optionally includecontrolling the porosity of the crack mitigating layer as otherwisedescribed herein. The method may further include controlling theintrinsic film stresses of the crack mitigating layer and/or the filmthrough control of deposition and fabrication processes of the crackmitigating layer.

The method may include disposing an additional film, as describedherein, on the glass substrate 120. In one or more embodiments, themethod may include disposing the additional film on the glass substratesuch that the additional film is disposed between the glass substrate120 and the crack mitigating layer 130, between the crack mitigatinglayer 130 and the film 110 or, such that the film 110 is between thecrack mitigating layer 130 and the additional film. Alternatively, themethod may include disposing the additional film on the opposite majorsurface of the glass substrate 120 from the surface on which the film isdisposed.

In one or more embodiments, the method includes strengthening the glasssubstrate 120 before or after disposing the crack mitigating layer 130,film 110 and/or an additional film on the glass substrate. The glasssubstrate 120 may be strengthened chemically or otherwise. The glasssubstrate 120 may be strengthened after disposing the crack mitigatinglayer 130 on the glass substrate 120 but before disposing the film 110on the glass substrate. The glass substrate 120 may be strengthenedafter disposing the crack mitigating layer 130 and the film 110 on theglass substrate 120 but before disposing an additional film (if any) onthe glass substrate. Where no additional film is utilized, the glasssubstrate 120 may be strengthened after disposing the crack mitigatinglayer 130 and the film 110 on the glass substrate.

The following examples represent certain non-limiting embodiments of thedisclosure.

Examples 1A-1E

Examples 1A-1E were formed by providing glass substrates that included acomposition of 61 mol %≦SiO₂≦75 mol %; 7 mol %≦Al₂O₃≦15 mol %; 0 mol%≦B₂O₃≦12 mol %; 9 mol %≦Na₂O≦21 mol %; 0 mol %≦K₂O≦4 mol %; 0 mol%≦MgO≦7 mol %; 0 mol %≦CaO≦3 mol %, and 0 mol %≦SnO₂≦1 mol %. The glasssubstrates had a thickness of 0.7 mm. The glass substrates werestrengthened by ion exchange to provide a surface compressive stress(CS) of about 690 MPa and a compressive depth of layer (DOL) of about 24μm. The ion-exchange process was carried out by immersing the glasssubstrate in a molten potassium nitrate (KNO₃) bath that was heated to atemperature in the range from about 350° C. to 450° C. The glasssubstrates were immersed in the bath for a duration of 3-8 hours toachieve the surface CS and compressive DOL. After completing the ionexchange process, the glass substrates of Examples 1A-1E were cleaned ina 2% concentration KOH detergent solution, supplied by Semiclean KG,having a temperature of about 50° C.

A crack mitigating layer including a plasma-polymerized fluoropolymerwas disposed on the strengthened glass substrates of Examples 1C-1Eusing an ICP chamber. The crack mitigating layer was deposited in a 60second deposition process at a temperature of about 25° C. using amixture of C₄F₈ gas and H₂ gas flowed at 40 sccm and 20 sccm,respectively, at a pressure of about 5 mT, with 1500 W 13.56 MHz RF onthe coil and 50 W 13.56 MHz RF on the platen. Prior to combination witha film, the surface energy of the crack mitigating layer was measured inthe range from about 19 mJ/m² to about 24 mJ/m². The surface energy wasmeasured by using contact angle measurements using DI water, hexadecaneand diodomethane. A film including Cr was disposed on each of Examples1B-1E using an e-beam evaporation process. Comparative Example 1A didnot include a crack mitigating layer or a film and Comparative Example Bincluded a film but no crack mitigating layer. Prior to deposition ofthe film on Examples 1C-1E, each of Examples 1A-1E was heated to about120° C. under a pressure of about 2×10⁻⁷ torr and thereafter cooled toroom temperature. The thickness measurements provided in Table 1 weremeasured by spectroscopic ellipsometry.

TABLE 1 Examples 1A-1E. Crack Mitigating Film Example Layer ThicknessThickness 1A None None (comparative) 1B none 30 nm (comparative) 1C 6 nm30 nm 1D 6 nm 30 nm 1E 6 nm 30 nm

Ring-on-ring load to failure testing was used to demonstrate theretention of average flexural strength of Examples 1A-1E, as shown inFIG. 6. For ring-on-ring load to failure testing, the side with the filmand/or crack mitigating layer was in tension. The ring-on-ring load tofailure testing parameters included a contact radius of 1.6 mm, across-head speed of 1.2 mm/minute, a load ring diameter of 0.5 inches,and a support ring diameter of 1 inch. Before testing, an adhesive filmwas placed on both sides of the sample being tested to contain brokenglass shards.

As illustrated in FIG. 6, the addition of a crack mitigating layerresulted in articles that retained about the same average flexuralstrength as glass substrates without a crack mitigating layer or film(Comparative Example 1A). Moreover, the articles with a crack mitigatinglayer exhibited greater average flexural strength than the strengthenedand non-strengthened glass substrates with only a film and no crackmitigating layer (i.e. Comparative Example 1B) which exhibited asubstantial reduction in the average flexural strength.

Example 2: Nanoporous Crack Mitigating Layer

Examples 2A-2G were made by providing 0.7 mm thick ion-exchangestrengthened aluminosilicate glass substrates. The glass substrateincluded a composition of 61 mol %≦SiO₂≦75 mol %; 7 mol %≦Al₂O₃≦15 mol%; 0 mol %≦B₂O₃≦12 mol %; 9 mol %≦Na₂O≦21 mol %; 0 mol %≦K₂O≦4 mol %; 0mol %≦MgO≦7 mol %; 0 mol %≦CaO≦3 mol %, and 0 mol %≦SnO₂≦1 mol %. Theglass substrates were ion-exchanged in a KNO₃ molten salt bath having atemperature of about 350-450° C. for 3-8 hours. The ion-exchanged glasssubstrates had a compressive stress of about 687 MPa and an ion-exchangedepth of layer of about 24 microns. The glass substrates were thencleaned in a KOH detergent solution (1-4% Semiclean KG), having atemperature of about 50-70° C. with ultrasonic agitation at 40-110 KHz,rinsed in DI water with ultrasonics in the same frequency range, anddried.

The glass substrate of Example 2A was left bare, with no layers or filmsdisposed thereon. A nanoporous SiO₂ layer was deposited on each of theglass substrates of Examples 2B, 2C, 2F and 2G using resistive thermalevaporation of a SiO precursor material at a deposition rate of 5angstroms/second, a deposition pressure of 7.3×10⁻⁴ Torr, an oxygen flowrate of 100 sccm, an argon flow rate of 100 sccm, and a substratetemperature of initially about 25° C., which increased up to about 50°C. during deposition, due to the heat generated by the depositionprocess. The resulting nanoporous SiO₂ layer had a refractive index of1.38 at 550 nm wavelength which leads to an estimated porosity of 21%.The nanoporous SiO₂ layer was measured to have an elastic modulus of 20GPa using nanoindentation. Examples 2B and 2F included a nanoporous SiO₂layer having a thickness of about 200 nm and Examples 2C and 2G includeda nanoporous SiO₂ layer having a thickness of about 500 nm.

The glass substrates of Example 2D-2E (which did not include ananoporous layer) and Examples 2F and 2G (which each included ananoporous layer) were further coated with an indium-tin-oxide (ITO)film having a thickness of about 100 nm. The ITO films were formed usinga sputtering process and a KDF, model 903i, ITO coating system. Asputtering target of SnO₂:In2O3=10:90 (by weight), also supplied by KDFwas utilized. The ITO films were sputtered at a pressure of 15 mtorrwith 5 sccm flow of 90:10 mixed Ar:O₂, 95 sccm Ar flow, and 1000 W DCpower. After deposition, Examples 2E-2G were annealed at 200 C for 60min in air. Example 2D was not annealed. Table 2 summarizes theattributes and processing of Examples 2A-2G.

TABLE 2 Examples 2A-2G. Nanoporous SiO₂ Layer ITO Film AnnealingAnnealing Example Thickness Thickness Temperature Time Example 2A NoneNone N/A N/A (comparative) Example 2B 200 nm None N/A N/A (comparative)Example 2C 500 nm None N/A N/A (comparative) Example 2D None 100 nm NoneN/A (comparative) Example 2E None 100 nm 200° C. 60 min (comparative)Example 2F 200 nm 100 nm 200° C. 60 min Example 2G 500 nm 100 nm 200° C.60 min

The average flexural strength of Examples 2A-2G was evaluated in thesame manner as Examples 1A-1E. As shown in FIGS. 7 and 8, Examples 2Fand 2G (which each included a vapor-deposited nanoporous SiO₂ layerdisposed between the glass substrate and the ITO film) exhibitedimproved strength over Examples 2D and 2E (which included only an ITOfilm). Example 2D and 2E also exhibited a substantial reduction in theaverage flexural strength over Example 2A (which was a bare glasssubstrate). Examples 2B and 2C, which included no ITO film exhibitedabout the same average flexural strength as Example 2A, indicating thenanoporous SiO₂ layer did not degrade the strength of the glasssubstrate.

Examples 2D, which included 100 nm ITO film alone and was annealed,lowered the Weibull characteristic strength of the article to about 106kgf. The addition of the 200-500 nm nanoporous SiO₂ layer between theglass substrate and 100 nm ITO film (with the same annealing cycle), inExamples 2F and 2G, increased the characteristic flexural strength to175-183 kgf.

In experimental screening, the ITO films deposited on top of thenanoporous SiO₂ layers exhibited comparable resistivity levels as theITO films deposited directly on the glass substrate (with no interveningnanoporous SiO₂ layer). Sheet resistance ranged from 35-95 ohms/squarefor Examples 2D-2G (which corresponds to resistivity less than about10×10⁻⁴ ohm-cm).

Example 3: Nanoporous Inorganic Crack Mitigating Layer with AluminumOxynitride Film

Examples 3A-3B were made by providing 1.0 mm thick ion-exchangestrengthened aluminosilicate glass substrates. The glass substrateincluded a composition of 61 mol %≦SiO₂≦75 mol %; 7 mol %≦Al₂O₃≦15 mol%; 0 mol %≦B₂O₃≦12 mol %; 9 mol %≦Na₂O≦21 mol %; 0 mol %≦K₂O≦4 mol %; 0mol %≦MgO≦7 mol %; 0 mol %≦CaO≦3 mol %, and 0 mol %≦SnO2≦1 mol %. Theglass substrates were ion-exchanged in a KNO₃ molten salt bath having atemperature of about 350-450° C. for 3-8 hours to provide strengthenedglass substrates. The strengthened glass substrates had a compressivestress of about 885 MPa and an ion-exchange depth of layer of about 42microns. The glass substrates were then cleaned in a KOH detergentsolution (1-4% Semiclean KG), having a temperature of about 50-70° C.with ultrasonic agitation at 40-110 KHz, rinsed in DI water withultrasonics in the same frequency range, and dried.

Five glass substrates of Comparative Example 3A were left bare, with nolayers or films disposed thereon. A nanoporous SiO₂ layer was depositedon five glass substrates of Example 3B in a vacuum chamber usingresistive thermal evaporation of a SiO precursor material at adeposition rate of 5 angstroms/second, a deposition pressure of 9.0×10⁻⁴Torr, an oxygen flow rate of 150 sccm, an argon flow rate of 100 sccm,and a substrate temperature of initially about 25° C., which increasedup to about 50° C. during deposition, due to the heat generated by thedeposition process. The five samples of Example 3B were then furthercoated with 2000 nm thick AlO_(x)N_(y) films by DC reactive sputteringfrom an aluminum target at a pressure of about 0.75 mTorr in thepresence of argon flowed at a rate of 115 sccm, nitrogen flowed at arate of 50 sccm and oxygen flowed at a rate of 4 sccm. DC power wassupplied at 4000 W. The AlO_(x)N_(y) film was formed at a depositionrate of about 70 angstroms/minute. Table 3 summarizes the attributes andaverage strength values of Examples 3A-3B. As can be seen in Table 3,the average strength of the uncoated glass samples (Comparative Example3A) from this set was about 330 kgf, in this case calculated as a meanvalue of the five tested samples in terms of RoR load to failure. Theaverage strength of the samples of Example 3B was about 391 kgfConsidering the standard deviations of the average strength values, oneof ordinary skill in the art can readily understand that the strengthdistributions of these two samples sets (Comparative Example 3A andExample 3B) are statistically similar, or substantially the same.Weibull distribution analysis yields a similar statistical conclusion.As illustrated by Comparative Example 2B, similar 2000 nm thickAlO_(x)N_(y) films disposed directly onto similar glass substratesyielded RoR average load to failure values of about 140-160 kgf. Thus,the crack mitigating layer of Example 3B led to a substantialimprovement in the coated glass strength, relative to the same orsubstantially identical articles made without the crack mitigatinglayer.

TABLE 3 Examples 3A-3B. Average Strength Std. Nanoporous (Mean LoadDeviation SiO₂ Layer AlO_(x)N_(y) Film to Failure of Load to ExampleThickness Thickness in RoR, kgf) Failure, kgf Example 3A None None 33028.1 (comparative) Example 3B 2000 nm 2000 nm 391 71.5

Example 4: Crack Mitigating Layer Developed from Etchant Gas

Examples 4A-4B3 were made by providing 0.7 mm thick glass substratesthat are commercially available under the trademark Eagle XG®, fromCorning Incorporated. The glass substrates were then cleaned in a KOHdetergent solution (1-4% Semiclean KG), having a temperature of about50-70° C. with ultrasonic agitation at 40-110 KHz, rinsed in DI waterwith ultrasonics in the same frequency range, and dried. Thereafter, thesubstrate was exposed to an oxygen plasma generated by Branson ICP, for300 seconds at 1.2 torr, 300 sccm of oxygen flowed at 500 W.

The glass substrates of Example 4A were left bare, with no layers orfilms disposed thereon. The glass substrates of Examples 4B1-4B3included a crack mitigating layer developed by plasma-assisted exposureto a CF₄ etchant gas in an ICP chamber at a pressure of approximately 50mTorr. The crack mitigating layers were developed on the glasssubstrates of Examples 4B1-4B3 by 6 s, 60 s, and 600 s exposure to theCF₄ etchant, respectively.

The surfaces of the glass substrates of Examples 4A-4B3 were measuredusing XPS to assess surface composition. The results of the XPSmeasurements are depicted in FIG. 11. Example 4A, serving as thecontrol, demonstrates relatively high levels of boron, oxygen, andsilicon, indicative of the substrate glass composition containingappreciable amounts of SiO₂ and B₂O₃. As shown by FIG. 11, the glasssubstrates etched with CF₄, Examples 4B1-4B3, demonstrate progressivelylower levels of oxygen, silicon and boron with increasing etchantexposure times. In addition, the fluorine, calcium and magnesium levelsincrease in these samples as a function of etchant exposure times.Together, this data demonstrates that plasma-assisted etching of theseglass substrates with CF₄ has fluorinated the surface of thesesubstrates, leaving AlF_(x), CaF_(x) and MgF_(x) compounds andpreferentially removing SiO₂ and B₂O₃ from the surface. These AlF_(x),CaF_(x) and MgF_(x) metal fluorides make up the crack mitigating layerdeveloped on these glass substrates.

Example 5: Adhesive Energies of Glass Substrates with Crack MitigatingLayers Developed Through Plasma-Assisted Fluorination

Examples 5A1-5A3 were made by providing the same glass substrates aswere used in Example 4. Eagle XG glass. The glass substrates were thencleaned as provided above in Example 4.

The glass substrates of Example 5A1 included a crack mitigating layerdeveloped by plasma-assisted exposure to a CF₄ etchant gas in an ICPchamber at a pressure of approximately 50 mTorr. Carbon coverage of thesubstrates of Example 5A1 was measured at approximately 22%. The glasssubstrates of Examples 5A2 included a crack mitigating layer developedby plasma-assisted exposure to a 30 parts CF₄ etchant gas and 10 partsC₄F₈ polymer-forming gas in an ICP chamber at a pressure ofapproximately 50 mTorr. Carbon coverage of the substrates of Example 5A2was measured at approximately 79%, evidencing the formation of afluorocarbon polymer layer on the surface of the glass substrate.Finally, the glass substrates of Example 5A3 included a crack mitigatinglayer developed by plasma-assisted exposure to a CF₄ etchant gas in anRIE chamber at a pressure of approximately 50 mTorr. Carbon coverage ofthe substrates of Example 5A3 was measured at approximately 9%.

The glass substrates of Examples 5A1-5A3 with crack mitigating layersformed via plasma-assisted fluorination (i.e., carriers) were thenbonded to glass substrates comparable in composition to the carriersubstrate. These laminated articles were then subjected to testingcommensurate with Equation (11) to obtain adhesive energies indicativeof the adhesive strength of the crack mitigating layers. The results ofthese measurements are depicted in FIG. 12 as a function of annealingtemperature. This comparison provides an indication of the adhesiveenergy after exposure to typical post-processing temperatures. Inparticular, some of the treated substrates of Examples 5A1-A3 weresubjected to annealing at various temperatures for 10 minutes tosimulate elevated temperatures associated with film deposition over thecrack mitigating layer and/or thermal processing associated withpost-manufacturing thermal processing of the substrate associated with aparticular application. As the results demonstrate, all samplesdemonstrate relatively moderate adhesive energies of approximately 500mJ/m² or less up to 400° C., indicative of crack mitigating layers thatwill aid in the retention of glass substrate strength. Further, theExample 5A2 sample containing the fluorocarbon layer demonstrates nodetrimental increase in adhesive energy up to 600° C.

Example 6: Adhesive Energies of Glass, Alumina and Silica Surfaces withCrack Mitigating Layers Developed Through Plasma-Assisted Fluorinationand Metal Fluoride Deposition

Examples 6A1-A3, 6B and 6C were made by providing the same substrates asExamples 4 and 5. The substrates were cleaned in the same manner asExamples 4 and 5.

The glass substrates of Example 6A1 included a crack mitigating layerdeveloped by plasma-assisted exposure to a CF₄ etchant gas in an ICPchamber at a pressure of approximately 50 mTorr. The surface of theglass substrates of Example 6A2 was first modified by the deposition ofa SiO₂ layer before a crack mitigating layer was developed byplasma-assisted exposure to a CF₄ etchant gas in an ICP chamber at apressure of approximately 50 mTorr. The SiO₂ layer (about 100-130 nmthickness) was developed by plasma-enhanced chemical vapor deposition(“PECVD”). Similarly, the surface of the glass substrates of Example 6A3was first modified with the deposition of an Al₂O₃ layer before a crackmitigating layer was developed by plasma-assisted exposure to a CF₄etchant gas in an ICP chamber at a pressure of approximately 50 mTorr.The Al₂O₃ layer (about 3 nm thickness) was developed by reactivesputtering. Finally, the glass substrates of Examples 6B and 6C eachincluded a crack mitigating layer of CaF₂ and MgF₂, respectively,developed by e-beam evaporation. The CaF₂ and MgF₂ layers were each setto a thickness of about 20 nm.

The glass substrates of Examples 6A1-A3, 6B and 6C with crack mitigatinglayers formed via plasma-assisted fluorination or as discrete metalfluoride layers via e-beam evaporation (i.e., carriers) were then bondedto glass substrates comparable in composition to the carrier substrate.These laminated articles were then subjected to testing commensuratewith Equation (11) to obtain adhesive energies indicative of theadhesive strength of the crack mitigating layers. The results of thesemeasurements are depicted in FIG. 13 as a function of annealingtemperature. In particular, some of the treated substrates of Examples13A1-A3, 13B and 13C were subjected to annealing at various temperaturesfor 10 minutes to simulate elevated temperatures associated with filmdeposition over the crack mitigating layer and/or thermal processingassociated with post-manufacturing thermal processing of the substrateassociated with a particular application.

As the results in FIG. 13 demonstrate, all samples demonstraterelatively moderate adhesive energies of approximately 500 mJ/m² or lessup to 300° C., indicative of crack mitigating layers that will aid inthe retention of glass substrate strength. In comparing the adhesiveenergy data associated with Examples 6A1-A3, it is apparent that theCF₄-treated glass exhibits relatively low adhesive energies up to about500° C., whereas the CF₄-treated SiO₂ and Al₂O₃-coated glass experiencesa sharp increase in adhesive energy at 300 and 400° C., respectively.The implication is that fluorination of glass (Example 6A1) effectivelymoderates the adhesive energy up to 500° C. whereas fluorination of SiO₂and Al₂O₃ (Examples 6A2 and 6A3) is not as beneficial. As such, thefluorination of other components in the glass (not SiO₂ and Al₂O₃)appears to provide beneficial adhesive energy stabilization as afunction of temperature. Those “other components” in the glass arebelieved to be metal oxides, e.g., CaO, MgO, and others. It follows thatthe glass substrates in Examples 6B and 6C with discrete CaF₂ and MgF₂crack mitigating layers, respectively, exhibit adhesive energies at nohigher than approximately 500 mJ/m² up to 600° C.

Example 7: Ring-On-Ring Strength of Glass Substrates with e-BeamDeposited CaF₂ Crack Mitigating Layers and a Cr Film

Examples 7A, 7B, and 7C1-C4 were made by providing 1.0 mm thickion-exchange strengthened alkaline earth boro-aluminosilicate glasssubstrates. The glass substrate included a composition of at least about50 mol % SiO₂, at least about 10 mol % R₂O (which includes Na₂O), Al₂O₃,wherein −0.5 mol %≦Al₂O₃(mol %) —R₂O(mol %)≦2 mol %; and B₂O₃, whereinB₂O₃(mol %) —(R₂O(mol %) —Al₂O₃(mol %))≧4.5 mol %. The glass substrateswere ion-exchanged in a KNO₃ molten salt bath having a temperature ofabout 350-450° C. for 3-8 hours. The ion-exchanged glass substrates hada compressive stress of about 883 MPa and an ion-exchange depth of layerof about 41.3 microns. The glass substrates were then cleaned in a KOHdetergent solution (1-4% Semiclean KG), having a temperature of about50-70° C. with ultrasonic agitation at 40-110 KHz, rinsed in DI waterwith ultrasonics in the same frequency range, and dried.

The glass substrates of Example 7A were left bare, with no crackmitigating layers or films disposed thereon. The glass substrates ofExample 7B were prepared with a 3000 Å Cr film, but no crack mitigatinglayer. The Cr film was deposited by an e-beam evaporative technique. Theglass substrates of Example 7C1-C4 each included a CaF₂ crack mitigatinglayer, disposed on the surface of the glass substrate by e-beamevaporative techniques. The thickness of the CaF₂ crack mitigating layerin Examples 7C1-C4 was 200, 500, 1000 and 2000 Å, respectively. Further,the substrates of Example 7C1-C4 also included a 3000 Å Cr film.

Ring-on-ring load to failure testing was used to demonstrate theretention of average flexural strength of Examples 7A, 7B and 7C1-C4, asshown in FIG. 14. For ring-on-ring load to failure testing, the sidewith the film and/or crack mitigating layer was in tension. Thering-on-ring load to failure testing parameters included a contactradius of 1.6 mm, a load ring diameter of 0.5 inches, and a support ringdiameter of 1 inch. The test procedure was performed according to ASTMC1499. Before testing, an adhesive film was placed on both sides of thesample being tested to contain broken glass shards.

As illustrated in FIG. 14, the addition of a CaF₂ crack mitigating layerresulted in articles (Examples 7C1-7C4) that retained about the sameaverage flexural strength as glass substrates without a CaF₂ crackmitigating layer or Cr film (Comparative Example 7A). Moreover, thearticles with a CaF₂ crack mitigating layer exhibited greater averageflexural strength and characteristic strength values (σ_(o)) than thestrengthened and non-strengthened glass substrates with only a Cr filmand no crack mitigating layer (i.e., Comparative Example 7B) whichexhibited a substantial reduction in the average flexural strength andcharacteristic strength.

Example 8: Ring-On-Ring Strength of Glass Substrates with e-BeamDeposited BaF₂ Crack Mitigating Layers and a Cr Film

Examples 8A, 8B, and 8C1-C2 were made by providing the same substratesas Example 14. The glass substrates of Example 8A were left bare, withno crack mitigating layers or films disposed thereon. The glasssubstrates of Example 8B were prepared with a 3000 Å Cr film, but nocrack mitigating layer. The Cr film was deposited by an e-beamevaporative technique. The glass substrates of Example 8C1-C2 eachincluded a BaF₂ crack mitigating layer, disposed on the surface of theglass substrate by e-beam evaporative techniques. The thickness of theBaF₂ crack mitigating layer in Examples 8C1-C2 was 500 and 1000 Å,respectively. Further, the substrates of Example 8C1-C2 also included a3000 Å Cr film.

Ring-on-ring load to failure testing was used to demonstrate theretention of average flexural strength of Examples 8A, 8B and 8C1-C2, asshown in FIG. 15. For ring-on-ring load to failure testing, the sidewith the film and/or crack mitigating layer was in tension. Thering-on-ring load to failure testing parameters included a contactradius of 1.6 mm, a load ring diameter of 0.5 inches, and a support ringdiameter of 1 inch. The test procedure was performed according to ASTMC1499. Before testing, an adhesive film was placed on both sides of thesample being tested to contain broken glass shards.

As illustrated in FIG. 15, the addition of a BaF₂ crack mitigating layerresulted in articles (Examples 8C1-8C2) that retained about the sameaverage flexural strength as glass substrates without a BaF₂ crackmitigating layer or Cr film (Comparative Example 8A). Moreover, thearticles with a BaF₂ crack mitigating layer exhibited greater averageflexural strength and characteristic strength values (σ_(o)) than thestrengthened and non-strengthened glass substrates with only a Cr filmand no crack mitigating layer (i.e., Comparative Example 8B) whichexhibited a substantial reduction in the average flexural strength andcharacteristic strength.

Example 16: Ring-On-Ring Strength of Glass Substrates with e-BeamDeposited MgF₂ Crack Mitigating Layers and a Cr Film

Examples 9A, 9B, and 9C were made by providing the same substrates asExample 14. The glass substrates of Example 9A were left bare, with nocrack mitigating layers or films disposed thereon. The glass substratesof Example 9B were prepared with a 3000 Å Cr film, but no crackmitigating layer. The Cr film was deposited by an e-beam evaporativetechnique. The glass substrates of Example 9C each included a MgF₂ crackmitigating layer, disposed on the surface of the glass substrate bye-beam evaporative techniques. The thickness of the MgF₂ crackmitigating layer in Example 9 C was 1000 Å. Further, the substrates ofExample 9C also included a 3000 Å Cr film.

Ring-on-ring load to failure testing was used to demonstrate theretention of average flexural strength of Examples 9A, 9B and 9C, asshown in FIG. 16. For ring-on-ring load to failure testing, the sidewith the film and/or crack mitigating layer was in tension. Thering-on-ring load to failure testing parameters included a contactradius of 1.6 mm, a load ring diameter of 0.5 inches, and a support ringdiameter of 1 inch. The test procedure was performed according to ASTMC1499. Before testing, an adhesive film was placed on both sides of thesample being tested to contain broken glass shards.

As illustrated in FIG. 16, the addition of a 1000 Å-thick MgF₂ crackmitigating layer resulted in articles (Example 9C) that retained aboutthe same average flexural strength as glass substrates without a MgF₂crack mitigating layer or Cr film (Comparative Example 9A). Moreover,the articles with a MgF₂ crack mitigating layer exhibited greateraverage flexural strength and characteristic strength values (σ_(o))than the strengthened and non-strengthened glass substrates with only aCr film and no crack mitigating layer (i.e., Comparative Example 9B)which exhibited a substantial reduction in the average flexural strengthand characteristic strength.

Example 17: Ring-On-Ring Strength of Glass Substrates with e-BeamDeposited CaF₂ Crack Mitigating Layers and an ITO Film

Examples 10A, 10B, and 10C were made by providing the same substrates asExample 14.

The glass substrates of Example 10A were left bare, with no crackmitigating layers or films disposed thereon. The glass substrates ofExample 10B were prepared with a 1000 Å indium tin oxide (“ITO”) film,but no crack mitigating layer. The ITO film was deposited by DCsputtering from a 10:90 (by weight) SnO₂:In₂O₃ oxide target at apressure of 10 mTorr. The glass substrates of Example 10C each includeda CaF₂ crack mitigating layer, disposed on the surface of the glasssubstrate by e-beam evaporative techniques. The thickness of the CaF₂crack mitigating layer in Example 10C was 500 Å. Further, the substratesof Example 10C also included a 1000 Å ITO film.

Ring-on-ring load to failure testing was used to demonstrate theretention of average flexural strength of Examples 10A, 10B and 10C, asshown in FIG. 17. For ring-on-ring load to failure testing, the sidewith the film and/or crack mitigating layer was in tension. Thering-on-ring load to failure testing parameters included a contactradius of 1.6 mm, a load ring diameter of 0.5 inches, and a support ringdiameter of 1 inch. The test procedure was performed according to ASTMC1499. Before testing, an adhesive film was placed on both sides of thesample being tested to contain broken glass shards.

As illustrated in FIG. 17, the addition of a 500 Å-thick CaF₂ crackmitigating layer resulted in articles (Example 10C) that retained aboutthe same average flexural strength as glass substrates without a CaF₂crack mitigating layer or ITO film (Comparative Example 10A). Moreover,the articles with a CaF₂ crack mitigating layer exhibited greateraverage flexural strength and characteristic strength values (σ_(o))than the strengthened and non-strengthened glass substrates with only anITO film and no crack mitigating layer (i.e., Comparative Example 10B)which exhibited a substantial reduction in the average flexural strengthand characteristic strength.

Example 18: Ring-On-Ring Strength of Glass Substrates with e-BeamDeposited BaF₂ Crack Mitigating Layers and an ITO Film

Examples 11A, 11B, and 11C1-C2 were made by providing the same substrateas used in Example 17. The glass substrates of Example 11A were leftbare, with no crack mitigating layers or films disposed thereon. Theglass substrates of Example 11B were prepared with a 1000 Å indium tinoxide (“ITO”) film, but no crack mitigating layer. The ITO film wasdeposited by DC sputtering from a 10:90 (by weight) SnO₂:In₂O₃ oxidetarget at a pressure of 10 mTorr. The glass substrates of Examples11C1-C2 each included a BaF₂ crack mitigating layer, disposed on thesurface of the glass substrate by e-beam evaporative techniques. Thethickness of the BaF₂ crack mitigating layer in Examples 11C1-C2 was1000 and 2000 Å, respectively. Further, the substrates of Example11C1-C2 also included a 1000 Å ITO film.

Ring-on-ring load to failure testing was used to demonstrate theretention of average flexural strength of Examples 11A, 11B and 11C, asshown in FIG. 18. For ring-on-ring load to failure testing, the sidewith the film and/or crack mitigating layer was in tension. Thering-on-ring load to failure testing parameters included a contactradius of 1.6 mm, a load ring diameter of 0.5 inches, and a support ringdiameter of 1 inch. The test procedure was performed according to ASTMC1499. Before testing, an adhesive film was placed on both sides of thesample being tested to contain broken glass shards.

As illustrated in FIG. 18, the addition of a BaF₂ crack mitigating layerresulted in articles (Example 11C1-C2) that retained about the sameaverage flexural strength as glass substrates without a BaF₂ crackmitigating layer or ITO film (Comparative Example 11A). Moreover, thearticles with a BaF₂ crack mitigating layer exhibited greater averageflexural strength and characteristic strength values (σ_(o)) than thestrengthened and non-strengthened glass substrates with only an ITO filmand no crack mitigating layer (i.e., Comparative Example 11B) whichexhibited a substantial reduction in the average flexural strength andcharacteristic strength.

While the disclosure has been described with respect to a limited numberof embodiments for the purpose of illustration, those skilled in theart, having benefit of this disclosure, will appreciate that otherembodiments can be devised which do not depart from the scope of thedisclosure as disclosed herein. Accordingly, various modifications,adaptations and alternatives may occur to one skilled in the art withoutdeparting from the spirit and scope of the present disclosure.

We claim:
 1. A method of forming a laminate article comprising:providing a glass substrate having opposing major surfaces; disposing afilm having one or more functional properties a first opposing majorsurface forming an interface with the glass substrate; and controllingthe effective adhesion energy of the interface to less than about 4J/m².
 2. The method of claim 1, wherein controlling the effectiveadhesion energy comprises disposing a crack mitigating layer between thefilm and the glass substrate.
 3. The method of claim 2, wherein thecrack mitigating layer comprises a plasma-polymerized polymer, a silaneor a metal.
 4. The method of claim 3, wherein the plasma-polymerizedpolymer comprises one or more of a plasma-polymerized fluoropolymer, aplasma-polymerized hydrocarbon polymer, a plasma-polymerized siloxanepolymer and a plasma-polymerized silane polymer.